After being connected with a genealogist through ancestry.com I was delighted to be put in touch with the widow of Veryan Herbert who was a partner in both Yimkin Engineering and the sister company Gordon & Glynn Motors which was based next door in Cadogan Lane, London.
While there was no more news on my own chassis I was kindly given access to Veryan's motoring archive, including a photo of Veryan racing his own 1936 Riley Sprite Sports at a Silverstone Rally in 1957. Interestingly this car still exists and was recently sold in near original condition by Bonham's for a princely sum.
While both companies were run by his mother, Phyllis Herbert, Veryan retired from the business in 1960. Other precious items for the collection include a copy of the Yimkin Stage Tuning Specification and a Gordon & Glynn letterhead - but more of those is future posts.