It's very possible that this occurred during the IR35 shake-up - HMRC moved the liability for unpaid income tax (in a situation where a contractor was determined to be a de-facto employee) from limited company contractors themselves onto the client (the bank, in this case).

Banks had a very low risk appetite and so had to let these people go. What was going on in a lot of places was that vital staff who had to be dumped were intermediated by outsourcing providers. These companies either then paid the staff a very high salary and sold them in as temp labour, or took on the risk themselves and hired them as contractors for the same purpose.

This all made sense, but for a lot of contractors at the time, it felt like the apocalypse. The net effect was that HMRC exchanged flexibility in the labour market for immediate tax take. This may not have been a sensible decision.