The record, which dates back to 25 September 1924, was gained by British racing motorist and motoring journalist Sir Malcolm Campbell on a 12-cylinder Sunbeam at Pendine Sands race track (South Wales). He won the world speed records on land and on water several times.

Here is the text of the original document with the timing strips attached: 

One Kilometre from a Flying start.

To Westward in 15.01" = 239.84 K.P.H.

To Eastward in 15.60" = 230.77 K.P.H.

Mean        15.305" = 235.217 K.P.H.

The Timing Strips taken from the Electric Chronograph are attached. 

I claim on behalf of Captain Malcolm Campbell a world's record for this performance. 

Mr H. Gregory, a competent Surveyor, measured the distance and his certificate of Measurement is attached. 

Official Time Keeper to the R.A.C., for the Automatic Electric Chronograph of the Royal Automobile Club

Other Land Speed Record original documents will be accessible in the FIA e-library.