Ron wrote:

"The greatest recorded height by any pilot without a pressure cabin or even a pressure suit has been 49.500 feet by Britsh Sqaudron
Leader G. W. H. Reynolds, D.F.C. in a Spitfire Mark VC over Libya in 1942."

This is from the Guinness Book of World Records, edition 1980. Page 322, The Mechanical World.

Does anyone has more information about this feat? Couldn't find anything on the internet.

Undoubtedly one of the three Mk. VCs. specially modified by No 103 MU at Aboukir depot to intercept JU-86 recon a/c. They were a poor
man's version of the Mk.VI. They were given elongated wings, four bladed props and modified carbs, with armor and the regular guns
stripped out and replaced by a pair of .50 cals. They later installed a Merlin 61 in one of them, and reaching such a height would
probably require it.

Guy