It was a one-way - I'm using an award ticket for the return journey to DUB. There seems to be some glitches with the BA.com system for this particular flight. I've been checking it 2-3 times a day over the past three days - getting seemingly random results of anything from £195 to £4000. All for the same flight, same class, same connection in LHR. Right now it's coming up at £895 one way, DUB-LHR-HKG.

I already have the ticket booked through the travel agent, but am checking it out of curiosity more than anything else. I know one-way tickets are generally more expensive than a return, but this seemingly random pricing is very, very strange.