It was probably unfair of me to expect dialogue befitting James Bond to be spoken by junior staff within the walls of GCHQ. However, I did not expect "I'm sorry" to be the stock phrase - for those with a counter and untold patience, I'd be interested in knowing the final score.
Having got that off my chest, the plot was good but as is often the case with these six parters, it could easily have been accommodated in four.