The Dewar Trophy was a cup donated in the early years of the twentieth century by Sir Thomas R. Dewar, M.P. a member of parliament of the United Kingdom, to be awarded each year by the Royal Automobile Club (RAC) of England "to the motor car which should successfully complete the most meritorious performance or test furthering the interests and advancement of the [automobile] industry".

Dewar Trophy Winners
The trophy was won by:

• 1906 - Stanley twins for their land speed record in the Stanley Steamer
• 1908 - Cadillac, for parts interchangeability. The award was actually presented in 1909.
• 1913 - Cadillac for the electric starter and electric lights.

Dewar Trophy History
In February 1908, three Model Ks from the 1907 Cadillac production were released from the stock of Frederick Stanley Bennett (UK agent for Cadillac automobiles) at the Heddon Street showroom in London (these were engines Nos. 23391, 24111 and 24118).

The three cars, all registered in London under the numbers A2EO, A3EO and A4EO, were driven 25 miles to the Brooklands race track at Weybridge. There, the cars completed another 25 miles before being put under lock and key until Monday March 2, 1908 when they were released and disassembled completely.

Their 721 component parts were scrambled in one heap. Eighty-nine parts requiring extreme accuracy were withdrawn from the heap, locked away at the Brooklands club house and replaced with new parts from the Mr. Bennett's showroom stock.

A mechanic - Mr. E.O. Young - reassembled the cars with the help of his assistant - Mr. M.M. Gardner. Sometimes they had to work ankle-deep in water, using only wrenches and screwdrivers. The third car was re-assembled by Tuesday evening, March 10. By 2 p.m.

On Friday March 13 the three cars had completed the mandatory 500-mile run with singular regularity. Only one point was lost owing to a broken cotter pin in the ignition lever (promptly replaced from stock). During the event, it was reported that one of the sheds where the parts were stored became partly flooded during a heavy storm and some parts became rusted. Only oily rags could be used to remove all traces of the immersion.

On completion of the test, one of the cars was placed under lock and key where it remained until the start of the 2000-miles Reliability Trials, several months later. It came out the winner of the R.A.C. Trophy! Parts interchangeability could not have been demonstrated in any more convincing way.