O2's headquarters in Slough will be closed today as 3,000 staff take part in an Olympics flexible working pilot in preparation for the chaos expected when the London 2012 Games take place this summer.
Firms across the UK - particularly those in London and the south east - have been encouraged by the government and the Games' organisers to prepare for their operations being severely affected as a result of the Olympics.
Existing transport links are not expected to cope with the crowds generated by the Games and firms have been asked to consider remote and flexible working for their staff.
O2 employs 12,000 in the UK, so the Slough shutdown represents a quarter of its workforce. The O2 site is up the road from Dorney Reach where the Olympics rowing competition will take place.
O2 says the shutdown will be used to help measure the progress it has made in its ongoing company flexible working strategy. Staff will work from home, local cafes, O2 stores or partner offices. Operations will be "business as usual", says O2, with all meetings being conducted remotely.
Ben Dowd, O2 business director, said: "We believe a cultural step-change is underway affecting staff and businesses, as work increasingly becomes something we do, rather than a place that we go.
"Today's initiative is an opportunity for us to take the next step on our flexible working journey and tangibly demonstrate the opportunity and potential available to British businesses today."
Up to 800,000 spectators and 55,000 athletes, officials, organisers and press will be travelling to and from Olympic venues every day. The organisers have predicted that on 3 August 2012, the first day of the track and field events, there will be an extra three million trips made on top of the 12 million trips on public transport being made on an average London workday.