"tim..." writes:

I am personally struggling with why TfL needs 100 IT people, given
that the ticketing system is contracted out to Cubic and many back
office services (payroll etc) will be likewise.

you don't need 100 people to maintain their website, do they?

Who maintains the IT systems which provide passenger information and
tracking systems? Systems such as those which track the location of all
the TfL busses, operate the 'next bus' displays at stops and the systems
in the control and monitoring offices. Are these in-house or contracted
out?