I have just has a thought. The "Blue Watch" article starts off:

"Sunday October 9, 2005
The Observer

He was firefighter Aaron Roche, the first person to enter carriage 346A
of the 8.51am Piccadilly Line service from King's Cross after the 7
July bombs went off.
It was the 48th such service to leave London's busiest tube station
that morning, each carriage crammed with commuters, many reading the
newspaper coverage of London's Olympic triumph the previous day.
It had just turned 10am when Roche began striding along the dark tunnel
towards the stranded train."

Is it possible to find out the number of the 48th westbound service
through King's Cross?