Originally Posted by
ISTFlyer
SIN does not have central security, all security screening occurs at the gate. BA might force the OP to gate check the bags and they would refuse to check it till LHR and would check it till EDI.
Gate check is a funny thing. I flew SIN-LHR-GLA-KOI last month and was forced to gate check (not that I actually mind) at LHR. Luckily I took a picture of those case as the tag was only to GLA and on arrival, I asked about them and was told that I have to collect them from the belt and recheck for the last lag.
NOTE: May or may not be the same in OP's case from SIN, IDK.