SAd sad to see the last BA 74 head west , so many hours spent on them in my pax 'carer' taking me safely to literally the four corners of the world , I flew to every continent on them. A lot of years my first flight on one was Nov 1971 and last BA 747 trip was ORD LHR in 2017 . Looking back I flew on 74s belonging to AF, BA (and BOAC), CX, LH, MH (Malaysian) PA, QF, SQ,TW, UA . First and last on BA ( and more trips than all the others combined) , Jo'burg and back on the same plane , (luckily in F). best trip AF Beijing to CDG also in F in a -100 but AF knew how to do F class back then.
Being west of LHR then if they were on easterlies and heavy and a lot of inbounds I might have had a chance for a photo or westerlies the Cape Town departure barely made 6000 by Camberley if it was heavy . But today- no load no traffic and as DR says they will be at 5000 just a couple of miles from the airport and with no climb restriction above 6000 ft they will be a small spec by the time they are 20 miles west. Shame I would like to have bid it Adieu to the Queen of the skies, we will never see such an iconic airliner again