"Churchills Reply" – can anyone help me out with this Horsa serial?

All,

“Churchill’s Reply” adorned with the chalk number “5” is a well photo graphed Horsa glider that took part in the D-Day airborne landings in Normandy and landed near Ranville.

The two above photos are from the IWM and have been seen in numerous books on the subject of D-Day and the glider has been reproduced as a painting. However, all the published photos or copies available on-line are too small to be of use.

I’m after the serial number of this glider which is apparent in the second photo (B 5051) . I’ve emailed IWM asking for help and haven’t had a reply and not being in the UK I’m unable to go an look at the original.

So over to you – can anyone confirm the serial number? Through squinted eyes I looks sort of like “L?22?”.

The “5” has thrown me a bit as all the listed chalk numbers for D-Day are 2 or 3 digit in every book I have on the subject. Details of what, where, who would be useful too.