By Andrew Marr BBC News political editor

The opposition have got their teeth into a senior minister really for the first time since the election and are having a whale of a time.

They have done pretty well, I think, to get this evidence out of Tom Winsor, the rail regulator, and they are pursuing it very vigorously.

The general feeling around Westminster on Wednesday night was that he is not going up and he is not going out

But look at the actual pressures on Stephen Byers. Who would force him out?

Remember first he is a big mate of Tony Blair's, he is very close to Tony Blair.

His decision not to sack Jo Moore - the woman who wrote the famous e-mail on 11 September - which is probably the start of his recent troubles, is following what you could call the Blair doctrine: "Never let these swine in the media get a scalp or who knows where it might end."

So Blair will back him on that

Backbench popularity

Then, rather oddly for Stephen Byers, he is very popular at the moment on the Labour backbenches precisely because of what he has done over Railtrack.

They love this. They are quite happy to see shareholders unhappy and public money not going to bail them out.

So: a lot of pressure on him across the chamber; rather less pressure inside the government and the Labour Party.

My guess is he will survive.

The general feeling around Westminster on Wednesday night is that he's not going up and he's not going out.

Reshuffle prospects

Eventually a reshuffle will come round and all the usual games will be played about how many people are Blair loyalists and how many people are Gordon Brown types and all those things will be brought into consideration.

The transport secretary has clearly not had a happy time in his current job.

He had a reputation for being a sort of quiet, competent minister - no great fireworks but things were well under control when he was in charge.

Well, you look back at the last few weeks and probably you wouldn't say that today.