The average commute into London takes up to 90 minutes

It found delays which followed the October 2000 Hatfield rail crash, were damaging London's businesses and leaving employees stressed and tired.

Over 200 people from seven companies were interviewed last July as part of the survey by the University of Westminster and the British Council for Offices.

It found a quarter of people had changed the time they expected to arrive at work since the crash.

And those who were late because of train delays were likely to stay longer and take shorter breaks to make up the time.

If you are late to a meeting, it means everyone is behind for the day Professor Peter White, University of Westminster

Network Rail, which runs the UK's railways, said it could take until the end of the decade before punctuality returned to pre-Hatfield levels.

Typical train journeys into London were between an hour and 90 minutes long, the survey found.

Professor Peter White, from the University of Westminster, said employees were making adjustments "at the expense of their own personal time" to get the work done.

He added even small delays could disrupt a company's business and often meant meetings were delayed to wait for train users to arrive.

"It can have a real knock-on effect.