Passengers requiring police presence are a regular occurrence. As flygirl68 and paxagent (both BA staff who know facts rather than needing to speculate) have indicated they could either have been deportees (handled on a regular basis at LGW for Jamaican and/or Eastern European flights) or VIPs requiring escort. It's no big deal for either and something we as staff see on a daily basis.

You'd be surprised at some of the things we see and deal with on a daily basis.