Being such a draw in the capital ensured that these birds were well-photographed (the above from Chris Hinton) and after a bit of detective work (and jigsaw-puzzling), Andy Moon managed to piece together the full ring numbers. Bearded Tits often seem to travel in small groups, so it was perhaps not surprising that these birds had been ringed together, and with consecutive ring numbers.
L511927 and L511928 were originally ringed on 10th November 2012, 32km north of Hyde Park at Rye Meads, Hoddesdon. They were caught along with a single male, but weren't seen again after release, but there was a report of two females from Amwell on 14th November. Prior to that the last Bearded Tits ringed at Rye Meads was in 2002, although a ringed male was recaught there in February 2011, having been originally ringed at Haddiscoe Island, Norfolk.
Thanks to Des McKenzie for piecing the numbers together, Chris Hinton for the photo and Chris Dee (Rye Meads Ringing Group) for the ringing details.