No it wouldn't start, I tried removing all USB devices one at a time to check that. The message came after the booting up message but before the one about the RAID drives, both of which come before Windows starts. It just stopped having counted down to zero but didn't shut down.
There are a pair of USB ports at the front of the computer on the side. These have in the past taken some damage where my son kicked a memory stick plugged in there. The metal work in there is a bit bent etc.
I opened up the computer, hoovered out a bit of dust (having unblocked the hoover) and had a look at it. These two USB ports are part of one solid moulded bit of plastic that also has a headphone socket and a microphone (I think) socket. I traced the wires from this back to the motherboard and unplugged the pair that I thought were the USB pair (the ones with more wires) The computer now works again, so I guess that this was the problem and a workable solution.
Thanks.
