BAA reveals £230million Crossrail investment

Businesses clubbed together last autumn to agree a funding package for the project, which will link key London destinations such as the City, Canary Wharf and Heathrow from 2017.

But the exact nature of BAA's contribution, which will be paid in two instalments, was only revealed this week.

As part of the plan agreed last year, a third of the funding for the 118.5km line will come from the Government, with another third being provided by businesses and the remainder coming from fares.

But speculation over the availability of cash for the ambitious scheme was heightened by the banking crisis and fears of an oncoming recession.

The timing of the announcement seems designed to boost confidence in the commitment of corporations in the capital towards the long-awaited link, which received Royal Assent this summer.

Construction is still expected to begin in 2010.

Lord Adonis claimed BAA's pledge represented "a major step" towards the delivery of Crossrail.

He said: "Business has long been a strong advocate for Crossrail and this is borne out today.

"Trains will run four times an hour for most of the day - cutting journey times across London and the South East and significantly improving rail access to Heathrow for thousands of passengers and airport workers every day."

BAA's strategy director Mike Forster said: "This vital new link will directly connect the City and Canary Wharf to the airport, complementing our existing Heathrow Express service and taking thousands of cars off the roads.

"Crossrail will be crucial in keeping London and the UK globally competitive."