David Marlow, the editor of the Morini Club Magazine, surprised me (21-11-2012) with a page from the book:
“Veteran and Vintage Cars” by Peter Roberts (first published 1962).
It says that the valves of this car were desmodromically controlled.
The author (born 1925) might be too old to ask him for the very evidence.
Hope to find someone who might be able to resolve this mystery.
“Between 1901 and 1905 the Brushmobile electric car was developed using a Vauxhall Motors engine, although only six were built.
One of these six featured in the film Carry on Screaming.”
Source: http://en.wikipedia.org/wiki/Brush_Traction
So now we know that a Vauxhall engine was used, it must become easier to find the evidence:
Soon after becoming The Vauxhall Ironworks Company Limited in 1897, the company developed a single-cylinder petrol engine that was used to propel a small river launch named Jabberwock.
The early design seen in Jabberwock is thought to have been the inspiration for the 5hp engine used to power Vauxhall’s first production car, launched in mid-1903 as a direct result of the determination of the directors, F W Hodges and J H Chambers. The car depended on one horizontal cylinder …
Source: http://www.vauxhallcivicsociety.org.uk/history/vauxhall-motors/
Mystery busted
Source picture left: The Autocar, October 31st, 1903
The 5 and 6hp Vauxhalls had a single cylinder horizontal engine with the cylinder facing backwards. The inlet valve was in the cylinder head and was opened by atmospheric pressure against a very light spring, with a control which altered the spring tension. The exhaust valve was in the normal sidevalve configuration alongside the cylinder and was opened by a conventional cam.
Text: Nic Portway, author of the book “Vauxhall cars 1903 -1918”