| Description | Date | Identifier | |
| Cover note for a fortnightly report on the progress of design work. | 4th Oct 1934 | Box 30 \ 4 Scan304 | |
| Design position report detailing the status of various items for the 20/25 HP and Bentley chassis. | 4th Oct 1934 | Box 30 \ 4 Scan305 | |
| List of design modifications and their status for Bentley and Phantom II chassis. | 4th Oct 1934 | Box 30 \ 4 Scan306 | |
| List of design modifications and their completion status for the Spectre chassis. | 4th Oct 1934 | Box 30 \ 4 Scan307 | |
| List of design modifications and their current status for the Spectre Chassis. | 4th Oct 1934 | Box 30 \ 4 Scan308 | |
| Design position report detailing the status of items for the Spectre and Wraith chassis. | 4th Oct 1934 | Box 30 \ 4 Scan309 | |
| Design position report detailing the status of components for the Wraith Chassis and Phantom II Tank Engines. | 4th Oct 1934 | Box 30 \ 4 Scan310 | |
| Design position report for the P.V.G.II and Griffon engines, listing the status of various components. | 4th Oct 1934 | Box 30 \ 4 Scan311 | |
| Design position status report for the P.V.XII engine and single cylinder research projects. | 4th Oct 1934 | Box 30 \ 4 Scan312 | |
| Design position report detailing the status of various single-cylinder and general research projects. | 4th Oct 1934 | Box 30 \ 4 Scan313 | |
| Design position report detailing the status of components for the Kestrel and Goshawk engines. | 18th Oct 1934 | Box 30 \ 4 Scan314 | |
| Cover note for a fortnightly report on the progress of design work. | 18th Oct 1934 | Box 30 \ 4 Scan315 | |
| Design position report listing the status of various chassis components. | 18th Oct 1934 | Box 30 \ 4 Scan316 | |
| Status report on the future development of the Merlin 'E' and Buzzard engines. | 20th Jun 1935 | Box 30 \ 4 Scan317 | |
| Cover memo for a fortnightly report on the progress of design work. | 20th Jun 1935 | Box 30 \ 4 Scan318 | |
| List of modifications and their status for Bentley, 20/25 HP, and Phantom II Tank Engine chassis. | 20th Jun 1935 | Box 30 \ 4 Scan319 | |
| List of design positions and their current status for the Spectre Chassis. | 20th Jun 1935 | Box 30 \ 4 Scan320 | |
| List of design modifications and their completion status. | 20th Jun 1935 | Box 30 \ 4 Scan321 | |
| Design position report for the Spectre model, listing the status of various components. | 20th Jun 1935 | Box 30 \ 4 Scan322 | |
| Design position report detailing the status of various components for the Spectre and Wraith chassis. | 20th Jun 1935 | Box 30 \ 4 Scan323 | |
| List of items and their design positions for the Wraith Chassis. | 20th Jun 1935 | Box 30 \ 4 Scan324 | |
| Design position report on single cylinder and general research items. | 20th Jun 1935 | Box 30 \ 4 Scan325 | |
| Status report on single cylinder and general research projects for Exe, Merlin, and Kestrel engines. | 20th Jun 1935 | Box 30 \ 4 Scan326 | |
| Design position report detailing modifications and their status for the Merlin 'C.1' and 'C.2' engines. | 20th Jun 1935 | Box 30 \ 4 Scan327 | |
| Design position report detailing the status of various components for the Merlin C.2, Goshawk B, and Liquid Cooled Exe engines. | 5th Jul 1935 | Box 30 \ 4 Scan328 | |
| Cover letter for a fortnightly report on the progress of design work. | 5th Jul 1935 | Box 30 \ 4 Scan329 | |
| Design position report detailing modifications and their status for various chassis and engines. | 5th Jul 1935 | Box 30 \ 4 Scan330 | |
| Design position report listing the status of various components for the Spectre Chassis. | 3rd Jul 1935 | Box 30 \ 4 Scan331 | |
| Design position report for the Spectre Chassis, detailing the status of various modifications and investigations. | 3rd Jul 1935 | Box 30 \ 4 Scan332 | |
| Design status report for the Spectre Chassis, listing various items and their completion status. | 4th Jul 1935 | Box 30 \ 4 Scan333 | |
| Design position status report listing various components, including those for the Wraith chassis. | 25th Jun 1935 | Box 30 \ 4 Scan334 | |
| Design position status report on single-cylinder and general engine research projects. | 25th Jun 1935 | Box 30 \ 4 Scan335 | |
| Progress report on single cylinder, general research, and Kestrel engine projects. | 28th Jun 1935 | Box 30 \ 4 Scan336 | |
| Design position report on components for Merlin C.I, Merlin C.II, and Goshawk 'B' engines. | 28th Jun 1935 | Box 30 \ 4 Scan337 | |
| Design position report detailing modifications and status for the Goshawk 'B' and Liquid Cooled Exe engines. | 24th Jun 1935 | Box 30 \ 4 Scan338 | |
| Progress report on design work for the period starting 5.7.35. | 8th Aug 1935 | Box 30 \ 4 Scan339 | |
| Design position report on chassis modifications for Bentley and 20/25 HP models. | 8th Aug 1935 | Box 30 \ 4 Scan340 | |
| Design status report for Phantom II Tank Engines and Spectre Chassis, listing various modifications and their completion status. | 8th Aug 1935 | Box 30 \ 4 Scan341 | |
| Progress report on modifications and investigations for the Goshawk 'C' and Vulture engines. | 10th Dec 1935 | Box 30 \ 4 Scan342 | |
| Status report on the future development of the Merlin 'E' and Buzzard engines. | 14th Dec 1935 | Box 30 \ 4 Scan343 | |
| Instruction for designers to mark temporary experimental modifications as 'Not suitable for production'. | 14th Dec 1935 | Box 30 \ 4 Scan344 | |
| Cover memo for a fortnightly report on the progress of design. | 2nd Jan 1935 | Box 30 \ 4 Scan345 | |
| Design position report detailing the status of various components for the Bentley Chassis. | 24th Dec 1935 | Box 30 \ 4 Scan346 | |
| Design position report for the 25-30 HP chassis, sheet 2. | 24th Dec 1935 | Box 30 \ 4 Scan347 | |
| Design position report for the Phantom III Chassis, detailing the status of various components and modifications. | 31th Dec 1935 | Box 30 \ 4 Scan348 | |
| List of design changes and their completion status for the Phantom III model (sheet 4). | 30th Dec 1935 | Box 30 \ 4 Scan349 | |
| Design position list outlining the status of various components for the Wraith II chassis. | 31th Dec 1935 | Box 30 \ 4 Scan350 | |
| Status report on single cylinder and general research projects, detailing the progress on various engine components. | 31th Dec 1935 | Box 30 \ 4 Scan351 | |
| Design position summary for Kestrel and Merlin 'E' engine modifications. | 30th Dec 1935 | Box 30 \ 4 Scan352 | |
| Design position report detailing the status of modifications and components for the Merlin, Goshawk, and Vulture engines. | 31th Dec 1935 | Box 30 \ 4 Scan353 | |
| Letter from British Petroleum Co. proposing a comparative test of their petrol against Shell. | 9th Nov 1920 | Box 30 \ 5 Scan001 | |
| Proposal to test petrol from the British Petroleum Company, requesting 50 gallons for the tests. | 16th Nov 1920 | Box 30 \ 5 Scan002 | |
| To the HCH Laboratory regarding a sample of No.1 Petrol from the British Petroleum Company for analysis. | 24th Nov 1920 | Box 30 \ 5 Scan003 | |
| Notification of the receipt of 50 gallons of petrol from The British Petroleum Co. for the Experimental Department. | 26th Nov 1920 | Box 30 \ 5 Scan004 | |
| Report comparing petrol from British Petroleum Co. with Shell No.1 spirit, noting lower power and increased engine 'pinking'. | 13th Dec 1920 | Box 30 \ 5 Scan005 | |
| Test report on a sample of petrol, detailing its distillation, specific gravity, and rectification test results. | 25th Nov 1920 | Box 30 \ 5 Scan006 | |
| Use of 'Mex' motor spirit over 'Shell' for testing engines, considering cost and alternative suppliers like British Petroleum. | 27th Jan 1921 | Box 30 \ 5 Scan007 | |
| Unsatisfactory petrol quality and its impact on vehicle testing and carburation. | 9th Feb 1921 | Box 30 \ 5 Scan008 | |
| Laboratory report comparing the distillation properties and specific gravity of two petrol samples, 'Mex' and 'BP1'. | 11th Feb 1921 | Box 30 \ 5 Scan009 | |
| Tests on an engine misfire, investigating the effects of different fuels and heat application to the induction pipe. | 13th May 1921 | Box 30 \ 5 Scan010 | |
| Trial of a National Benzole 50/50 mixture from the British Petroleum Company. | 21th Aug 1922 | Box 30 \ 5 Scan011 | |
| Request to arrange for the collection of 83 empty B.P. petrol tins. | 19th Mar 1923 | Box 30 \ 5 Scan012 | |
| Letter to the British Petroleum Co. requesting a meeting to discuss a higher H.U.C.R. value fuel for the 'Miss England 11' engines. | 8th Dec 1930 | Box 30 \ 5 Scan013 | |
| Letter from the British Petroleum Company Ltd. regarding an appointment with Mr. Royce. | 11th Dec 1930 | Box 30 \ 5 Scan014 | |
| Letter regarding a preliminary test of two tyres from The India Tyre & Rubber Co. Ltd. | 8th Jan 1935 | Box 30 \ 5 Scan015 | |
| Letter from the India Tyre & Rubber Company Ltd. to Mr. Robotham regarding previous correspondence and a personal enquiry. | 9th Jan 1935 | Box 30 \ 5 Scan016 | |
| Letter to the Earl of Rothes regarding tyres, a squash court manufacturer, and declining a dinner invitation. | 14th Jan 1935 | Box 30 \ 5 Scan017 | |
| Letter to the Earl of Rothes regarding a business trip, a dinner, and the progress of a chassis body. | 21th Jan 1935 | Box 30 \ 5 Scan018 | |
| Letter regarding a brake issue on a Bentley, potentially caused by a choked drain hole. | 27th Jan 1929 | Box 30 \ 5 Scan019 | |
| Letter from a customer requesting an inspection of their car, speculating about issues caused by the chauffeur's use of the 'one shot' pedal. | 29th Jan 1935 | Box 30 \ 5 Scan020 | |
| Letter to The Earl of Rothes regarding the inspection of Capt. Dugdale's car and another chassis, B-10-DG. | 29th Jan 1935 | Box 30 \ 5 Scan021 | |
| Letter from India Tyre & Rubber Company Ltd. regarding the progress of bodywork on a car at Park Ward's. | 30th Jan 1935 | Box 30 \ 5 Scan022 | |
| Letter from India Tyre & Rubber Company regarding the seating trial for Mr. Thompson's chassis B.10.DG. | 2nd Feb 1935 | Box 30 \ 5 Scan023 | |
| Letter to the Earl of Rothes arranging potential meeting dates with Mr. Thompson. | 4th Feb 1935 | Box 30 \ 5 Scan024 | |
| Letter to the Earl of Rothes about scheduling a car seat trial at the Langham Hotel. | 8th Feb 1935 | Box 30 \ 5 Scan025 | |
| Letter to the Earl of Rothes regarding Captain Dugdale's car being in the Experimental Dept for a brake complaint. | 11th Feb 1935 | Box 30 \ 5 Scan026 | |
| Letter to The Earl of Rothes regarding the order of a 3½ litre Bentley Saloon and a modification for his father-in-law. | 18th Feb 1935 | Box 30 \ 5 Scan027 | |
| Letter from the India Tyre & Rubber Company Ltd. acknowledging correspondence. | 19th Feb 1935 | Box 30 \ 5 Scan028 | |
| Letter to a customer clarifying a part-exchange deal for a new Bentley or Rolls-Royce. | 19th Feb 1935 | Box 30 \ 5 Scan029 | |
| Letter to the Earl of Rothes regarding experimental water excluders and ordering new India tread tyres for a Bentley. | 4th Mar 1935 | Box 30 \ 5 Scan030 | |
| Order for tyres for Lord Rothes. | 4th Mar 1935 | Box 30 \ 5 Scan031 | |
| Letter from India Tyre & Rubber Company regarding Bentley water excluders and tyres. | 5th Mar 1935 | Box 30 \ 5 Scan032 | |
| Letter from India Tyre & Rubber Company Ltd. proposing a new chromium-plated Schrader 'Ezemount' valve fitting for Bentley cars. | 6th Mar 1935 | Box 30 \ 5 Scan033 | |
| Letter to The Earl of Rothes confirming a meeting and discussing work on noise insulation for Park Ward Bentley bodies. | 8th Mar 1935 | Box 30 \ 5 Scan034 | |
| Letter from India Tyre & Rubber Co. regarding the fitment and testing of new tyre types on a Bentley. | 14th Mar 1935 | Box 30 \ 5 Scan035 | |
| Letter concerning a Bentley chassis B-131-CW brake issue after washing and arranging a service visit. | 14th Mar 1935 | Box 30 \ 5 Scan036 | |
| Agreeing to supply the new type Schrader 'Ezemount' Valve Fitting with India tyres for Bentley vehicles. | 14th Mar 1935 | Box 30 \ 5 Scan037 | |
| Letter to The India Tyre & Rubber Co. Ltd. discussing a new valve assembly for Bentley tyres and requesting weights for extra low pressure tyres. | 14th Mar 1935 | Box 30 \ 5 Scan038 | |
| Letter from India Tyre & Rubber Company about the new Ezemount valve fitting for Bentley tyres and the specifications of tyres sent for testing. | 15th Mar 1935 | Box 30 \ 5 Scan039 | |
| Achieving car weight savings by utilising smaller wheels and tyres, referencing American practices. | 19th Mar 1935 | Box 30 \ 5 Scan040 | |
| Comparative table of wheel and tyre weights, and ground clearances for various car models. | 14th Mar 1935 | Box 30 \ 5 Scan041 | |
| Comparison of wheel and tyre weights in pounds for various models and sizes. | 19th Mar 1935 | Box 30 \ 5 Scan042 | |
| Letter from a tyre manufacturer discussing suitable tyre options and specifications for a Colonial Bentley. | 19th Mar 1935 | Box 30 \ 5 Scan043 | |
| Page 2 of a letter from India Tyre & Rubber Company Limited to W. A. Robotham. | 19th Mar 1935 | Box 30 \ 5 Scan044 | |
| Specification table detailing the dimensions and properties of various tyres. | 19th Mar 1935 | Box 30 \ 5 Scan045 | |
| Letter to a tyre manufacturer discussing the weights of various tyres for weight-saving purposes. | 20th Mar 1935 | Box 30 \ 5 Scan046 | |
| Letter from the India Tyre & Rubber Company discussing the weight difference between Bentley and Terraplane wheels and tyres. | 21th Mar 1935 | Box 30 \ 5 Scan047 | |
| Page 2 of a letter to W.A. Robotham discussing weight differences between types of tyres, wheels and hubs. | 21th Mar 1935 | Box 30 \ 5 Scan048 | |
| Letter from a tyre manufacturer discussing the suitability of 4-ply versus 6-ply low-pressure tyres for export vehicles. | 22th Mar 1935 | Box 30 \ 5 Scan049 | |
| Comparison of weights and dimensions for low-pressure tyres from manufacturers India, Goodyear, and Dunlop. | 22th Mar 1935 | Box 30 \ 5 Scan050 | |
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