Derek Branning has been revealed as Kat Moon's secret summer lover on 'EastEnders'.

Albert Square's resident villain was unveiled as loud-mouthed barmaid Kat's mystery fling in a drama-filled episode of the BBC One soap last night (20.12.12).

The shock reveal happened after months of speculation when Alfie Moon followed his unfaithful wife to the bedsit on George Street and confronted her about her affair.

After discovering a tenancy agreement to 'Branning' in the bedsit, scorned Alfie marched over to the Queen Vic to quiz the Branning brothers.

When he jumped to the conclusion her lover must be Max, a panic-stricken Kat eventually blurted out: ''It's him - it's Derek!''

Shane Richie recently revealed his distraught alter ego Alfie would start a fling with Roxy Mitchell (Rita Simons) in the wake of the heartbreaking revelation.

He told Digital Spy: ''I think Rita Simons is now playing a different kind of Roxy, as the character is seeing somebody who she could spend the rest of her life with.

''At the same time, though, Roxy is feeling a little bit insecure because this relationship has happened very quickly. Roxy worries that Alfie might be on the rebound and could end up going back to Kat.''