The moment a fire alarm forced Channel 4 off air in middle of interview with a Cabinet Minister

But when Channel 4 news presenter Krishnan Guru-Murthy interrupted Caroline Flint mid-interview it wasn't merely because he had heard enough from the housing minister.

A fire alarm had gone off  - which could be heard ringing in the background - in the ITN building and staff  were forced to evacuate.

Guru-Murthy was in the middle of an interview with Mrs Flint during Channel 4's 12 o'clock news bulletin when the emergency evacuation occurred.

Guru-Murthy was interviewing Caroline Flint when the station went off air

As penetrative sound became audible in the background Mr Guru-Murthy chipped in during the live video-link from Westminster.

He said: 'If I can just break off for a second you and our viewers may hear a fire alarm here in our building and I apologise for that. We are trying to find out whether it is real or not.'

Meanwhile Miss Flint made the uncharitable comment: 'It's not in our building so I won't worry about it.'

Mr Guru-Murthy then joked: 'I hope we don't have to run out in the middle of this interview.'

He continued the interview for another minute and a half with the sound of sirens in the background before eventually doing just that under the strict orders of his producers.

Interrupting Mrs Flint mid-flow, Guru-Murthy said: 'I'm sorry to have to cut you off but unfortunately the fire alarm means we do have some problems here at ITN this lunchtime.'

Channel 4 news said that the presenter was the last one out of the ITN building during the drill.

As the siren rang in the background Guru-Murthy said: 'We're going to take a break now. We may or may not return after that because we may actually have to evacuate the building.'

'This is the first certainly in my career,' he continued. 'When we do come back - IF we come back - we'll have the business news and more economic news for you.'

As the theme tune for Channel 4 News faded in Guru-Murthy was seen hurriedly standing up and removing his microphone as the lights fade out.

The station then cut to a pre-recorded documentary -  'Rome: The Model Empire'.

Channel 4 praised him for handling the situation with aplomb.

A spokesman said: 'This is certainly the first time this has happened in Krishnan's career.

'He was very professional but eventually had no choice but to abandon the bulletin.

'ITN had a fire alarm which turned out to be a false alarm. It is company policy to evacuate the building.

'We kept the programme going for as long as was sensible. Krishnan, who is so unflappable, told the viewers what was happening.'

Luckily for viewers desperate to find out what Flint had to say about the nation's housing woes, Channel 4 News allows viewers to catch up on any missed bulletins on its website.

Oxford-educated Mr Guru-Murthy spent 10 years at the BBC before moving to Channel 4 News in 1998.