Vodafone has announced it will move its global headquarters from Berkshire to London, after nearly 20 years.
Chief executive Vittorio Colao is among those moving from the Newbury campus to Paddington in October.
More than 3,000 staff will stay in Newbury, which will also remain as the headquarters for the UK division.
About 900 members of the global division, called Vodafone Group plc, are among those who will remain in Newbury.
Vodafone Group plc said the reason for the move was to be closer to the company's business partners and stakeholders.
Teams that will move include the corporate strategy, industrial relations and the media team.
It confirmed that about 200 staff from across the UK would relocate to the campus in the town to ensure it was fully occupied.
'Key centre'
Matthew Brearley, director of human resources, told the BBC that Vodafone was "absolutely committed" to Newbury.
He said: "The reason we are moving those people is for the executive committee to be close to the investors, to be close to their strategic partners who are typically based out of London, that's the key for them to have very close access to those people.
"When 200 people move out to the site in Paddington, 200 people will move in, because we will make sure this site is fully occupied. It's a key centre for us.
"What we constantly do is we always look at our property portfolio and if we have opportunities to move people here to our site... clearly it's in our intention to make sure its fully occupied."
A spokesman said: "The UK base will stay in Newbury and about a fifth of people will move, including the senior management team and certain areas of headquarter staff who can be closer to stakeholders."
Both Vodafone Group plc and Vodafone UK used to occupy more than 60 buildings scattered across the town but opened a purpose-built headquarters in Shaw, on the outskirts of Newbury in 2003.
