My very redundant and creaky spotting synapses recall the Arrow being out of sequence and allocated well ahead of BA's 757s.
You're no doubt correct, Tredders. I never was a spotter, but of course out-of-sequence registrations are not uncommon. Hardly surprising that someone claimed G-BIKE before the 757 allocations.
One that seems to have got away was G-AVRO; it went to a lowly Britannia 737.