I can certify that this thread now is reporting TWO separate incidents. The first involved a Flightline Bae146 that departed Manston on an EUJet flight, but didn't get as far as Dover, instead circled overhead for a while to try and fix the problem, and being unsuccessful returned and landed safely at Manston. This occurred at around 1715z Saturday 19th February.
I have since heard of a F100 positioning having a gear problem today, Sunday 20th Feb, but has now landed safely.
What was the F100 doing in LGW in the first place? Maintenance? Would explain why the Bae146 was operating on the Saturday.