Google is backing a return to the office with an investment that will expand its UK capacity by 50% and "reinvigorate" the work environment.
The search giant is spending £730m ($1bn) and expects headcount to rise from 6,400 to 10,000.
It is buying one of the London sites, Central Saint Giles, in which it is currently a tenant.
Google's UK boss Ronan Harris told the BBC the investment reflected the firm's faith in the office as a place of work.
"We want to reinvigorate the work environment. We're making this commitment to rebuild. We're buying these buildings and we're keen to see everybody come back in and see a vibrant workspace again," Mr Harris said.
As well as purchasing the Central Saint Giles site, Google said it would be undertaking a multi-million pound refurbishment of its offices there to ensure they were on a par with those in its new King's Cross development currently under construction.
That will provide more space so offices can be less densely populated, and will include collaboration spaces and "inclusive meeting rooms for hybrid working" as well as covered outdoor workspaces, the firm said.
Current government guidance remains to work from home where possible, but that - along with other government restrictions - will be reviewed on 26 January.
Eventually, Google wants the vast majority of its workforce to return to the office for three days a week.
But employers are feeling their way as the country emerges from two years of pandemic-enforced changes, during which many people adapted to completely different ways of working.
"I think the next two [years] will be an experiment where we try and figure out what hybrid and flexible actually mean," said Mr Harris.
"And I think it will differ from company to company and from role to role. I think it'll be a lot of trial and error over the next two years."
Chancellor Rishi Sunak welcomed Google's investment, describing it as "a big vote of confidence in the UK as a world-leading tech hub".
The employers group the CBI said a return to the workplace was vital for economic recovery, particularly for the UK's town and city centres.
Retail and hospitality businesses especially are eager for office staff to return to old habits, picking up coffees, sandwiches and shopping during the day and going out after work in the evening.
However, many employees don't want to return full time to the office and the number of days that employers require their staff to attend in person is emerging as a key point of difference in the recruitment process.
Neil Carberry from the Recruitment and Employment Confederation told the BBC: "Pay used to be the main lever employers could use in negotiations. Office attendance is now a major conversation between firms and potential employees."
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