Yes quite a rare event at LHR these days, but BA did one 2-3 weeks back. The old compass base was the real thing with no light fittings through the centre (though, if memory serves, it did have blue edge lights), or reinforcement in the concrete, though the newer one in Blk 43 is not so but has been deemed suitable for the job (Class 2??) after being checked periodically by boffins from DERA or whatever they are now (Qinetiq?).