G-AYSL. Sierra Lima, or as it was apparently universally known at BA/Airtours, "Spread Legs". An early onetime Pan Am aircraft, Dan-Air got it secondhand in 1971 and ran it themselves, but leased it to BA mainline in 1978 (when they seemed very short of aircraft, and were also using as much spare Airtours capacity on mainline routes as they were able) and to Airtours in 1979. When done at the end of the 1979 season it seems to have languished at Lasham for years, for sale without success, until finally broken up there.
The 707-123B behind it, ex-American Airlines, belonged to Transasian, which despite the name operated from Gatwick, but this was the second summer season it was leased to Air Malta. The following year, 1980, it was with Monarch, but that was its last duty.
The Caravelle in the foreground is, by most amazing coincidence, one of those two UTA Caravelle 10Rs discussed in the post above, which had been sold on in 1972 to Swiss charter operator SATA, later CTA. It did about 15 years with them and was a quite regular Gatwick visitor over the years, particularly on student charters.
May as well do the rest, in the background is a BA One-Eleven, not normally associated with Gatwick, but at the time for a few years they had a couple based there which did a small handful of European destinations in an attempt to stimulate Gatwick scheduled services for BA. Knowing how licensing worked then, it was likely an attempt to prevent B Cal getting such Gatwick routes.