Behind Enemy Lines is the 1554th episode of The Bill.
DC Spears and PC Smith are taken hostage when an armed bank raid goes terribly wrong. As SO19 units surround the building, Ch. Insp. Conway and Supt. Chandler arrive to negotiate with the two robbers, Dwight and Rollo. A tense stand-off ensues, and PC Smith realises the men are ex-soldiers and that they had help from one of the bank employees. Rollo shoots Dwight during an argument, and Chandler orders SO19 to storm the building despite Conway's objections. Spears is taken hostage, but Rollo turns the gun on himself when he realises there is no way out of the situation.
This was an extended feature-length episode.