By BBC News Online's political correspondent Nick Assinder.

It was New Labour which made the use of pagers an indispensable part of everyday life in Westminster.

All MPs were handed a "Millbank messenger" which was used to beam commands to them direct from the party headquarters - and they were ordered to wear them at all times.

If pagers could shout, these certainly would do.

It often appears that Labour MPs sit on the backbenches like robots, unable to move until they get a bleep from Millbank telling them what to do next.

The running joke in Westminster is that the messages often reads "breathe in, breathe out". And, of course, the troublemakers refuse to wear them.

It got so bad, with bleepers going off left right and centre in the chamber, that in March 1997, Speaker Betty Boothroyd issued a ruling that it was fine to have a vibrating pager, but not a bleeping one.

So it was a particularly sharp irony that it was the Tories who managed to vibrate first during Prime Minister's Question Time that Welsh first secretary Alun Michael had resigned - and get the message to their leader William Hague.

Blair did not know

Mr Blair clearly did not know and it not only landed him with his most embarrassing moment yet in the Commons but it also proved that, when it came to the battle of the bleepers, the Tories won hands down.

The incident also provided some of the best theatre seen in the Commons for years as over-excited MPs started rushing in and out of the chamber and frantically passing messages between themselves.

At one point things became so overheated with MPs yelling at each other across the floor that Speaker Betty Boothroyd stepped in to declare: "Some honourable members appear to be having apoplexy." And indeed they were.

It all started at 15.08 precisely, when Mr Michael stood up in front of the Cardiff assembly and dropped his resignation bombshell.

At the same time, the prime minister was in the Commons for his weekly clash with Mr Hague.

Suddenly Welsh spokesman Nigel Evans, who was keeping close tabs on the shenanigans in Cardiff, was vibrated with the news that Michael had quit.

He immediately leaned forward to alert his leader before running out of the chamber to confirm it. He swiftly returned to sit behind Mr Hague to give him the nod.

Seizing the moment

However, at the same time, 15.14 precisely, the Tory "war room" in Central Office also heard the news from Wales and immediately beamed messages to those sitting closest to Mr Hague - Ann Widdecombe, Andrew Mackay, Michael Ancram and John Whittingdale.

Mr Hague seized the moment, leapt to his feet to challenge Mr Blair - and the rest is now history.

But it left open the question of whether Mr Blair had known what his leader in Wales was doing. The simple answer is - yes and no...

Mr Michael had indeed called the prime minister at 1pm to tell him he intended to resign. But, crucially, he could not tell him exactly when that would happen.

The prime minister was confident it would be after the end of question time so was taken by surprise when the news broke.

When the news did break, MP Dennis MacShane was ordered to leave the chamber to confirm the story - he instantly fled, scattering backbenchers in his wake only to return with the bad news. But by then it was all too late.

So why didn't the world-famous Labour machine spare the prime minister his embarrassment by alerting him before the Tories got hold of the story?

Perhaps he wasn't wearing his Millbank messenger.