From the comment about Reg Cox...I think they were 2 special episodes to celebrate 15 of Eastenders.
Yes the bomb scare and most of the cast being locked inside the Vic for 2 episodes was to celebrate 15 years of Eastenders
Here was the Radio Times cover from that time: Feb 2000
This was actually a fold out cover which featured past & present cast members but I couldn’t find a picture with the full image unfolded.
The past & present cast that featured on the full folded out image were Michelle Collins, Martin Kemp, Todd Carty, Paul J Medford, Bill Treacher, John Altman, Wendy Richard, Steve McFadden, Gillian Taylforth, Jack Ryder, Lucy Speed, Adam Woodyatt