There are (or at least were up until a couple of years ago) Foot Guards and line infantry battalions under command (OPCOM) HQ London District. These Bns were based in the London area and were responsible for conducting ceremonial duties. During the operations in Iraq and Afghanistan, these Bns were (and probably still are) routinely re-subordinated to Type A (deployable) formations for deployment to Ops TELIC and HERRICK. I've lost track of which Bn is where at the moment, but 1 COLDM GDS may well be one of the two Foot Guards Bns based in London, but may well be under some sort of command (OPCOM/OPCOM/TACON/etc.) of a deployable Bde either in preparation for, returning from or currently deployed on Op HERRICK.