The Foreign Office has sold its embassy in Bangkok for £420m with the money slated to go towards modernising other British embassies around the world.

The sale to a consortium of businesses is the largest ever land deal in Thailand's history and the largest sale undertaken by the Foreign Office.

Diplomatic and consular staff in Bangkok will move to a new facility in the central business district by 2019. The current building was no longer fit-for-purpose, the Foreign Office claimed, with parts of the 1920s buildings no longer usable.

After an open competition, the sale went to Hongkong Land, a member of the Jardine Matheson Group, and Central Group.

"I'm determined to ensure that our diplomats have all the necessary tools to do their job effectively," Foreign Secretary Boris Johnson said of the sale. "This includes working in modern, safe, fit-for-purpose premises - not just in Bangkok but around the world.

"Our workforce in Bangkok will be moving into a state-of-the-art premises by 2019 and this can only enhance our trade links and bilateral relations in Thailand and throughout the region."

He called Thailand a "key partner for the UK's security and prosperity interests".

There was also a nod towards budget cut struggles, with permanent under-secretary Simon McDonald noting it was a "tight fiscal environment".

"This deal will [release] much-needed funds to modernise other embassies around the world, including in Cairo, New Delhi and Washington," McDonald said.