I took these photographs at the Richard Seaman Memorial Trophies meeting at Oulton Park in June 1982.
Number 31 is the 1939 Maserati 4CL of Dan Margulies and 25 is the 1954 Maserati 250F of David Sankey.
The Maserati 4CL is chassis number 1582, and I have come across this brief history of the car:
Maserati 4CL  (Toni Branca): Delivered 31 July 1946 to Guido Barbieri from Reggio Emilia, and raced in the 1946 Turin and Milan GPs. It is possible that the chassis was then used by Barbieri in his 1.5 litre Maserati 6C Sports Special, which first appeared in October 1946. The car reappeared in normal 4CL form in 1949 in the hands of Swiss Anton Branca, who raced it throughout 1949 and 1950. The car then passed through a variety of Swiss owners’ hands, at one stage fitted with a Ford V8 engine, before being campaigned in historic racing by Dan Margulies for more than 20 years, and being owned most recently by Klaus Edel and then Oliver Maierhofer. The car was for sale in early 2007.
Here's David Sankey at Knicker Brook in the Maserati 250F which is chassis number 2513, and you can read some of its history here.