Ian The Norwich Union Classic Car Run was one of the very early classic car events on a broad scale organised in the UK. It eventually became the Aviva Classic for 3 years between 2007 and 2009. It was run in 2010 unsponsored and then I believe dropped for lack of financial support. Plus there are now many many copy cats and other events which compete. The original Norwich Union car run goes back to the 1980's I recall running my first UK based PB in it (the wife drove the MGA) and then subsequent PB's and a J1 in later events. I do recall there we several starting points around the UK, finishing at Silverstone. I can probably dig out the original Brochures if you are interested.
Even better take a look at the following web page: www.masclassics.co.uk/history/mas_classic_history.php It will give you a pretty good overview of the event which started in 1986 - the year after I moved to the UK. I now recall we did the first "Norwich Union" in an MGB! Triple-M cars came later...
It might be worth checking with Barrie Gillies - he may be able to point you in the right direction. I think the car was owned by a guy in the Netherlands at about that time?