It will be spent on a 112-bed annex in Kiri Kiri prison in the country’s largest city Lagos, which will help accelerate the transfer of foreign criminals from the UK back to Nigeria.

The UK foreign secretary Johnson said: “As part of this agreement, eligible prisoners serving criminal sentences in Nigeria and the UK can be returned to complete their sentences in their respective countries.”

He added that the new facility is part of the compulsory prisoner transfer deal signed between the countries in 2014.

There were 270 Nigerian prisoners out of a total of 9,349 foreign nationals in UK prisons at the end of last year, according to the latest figures.

At the end of 2016 there were just under 10,000 foreign nationals in UK prisons, 19% of which were from African countries.

A Foreign Office spokesperson said: “The government believes that wherever possible foreign nationals should serve their sentences in their own country.

“Helping Nigeria to improve its prison conditions and increase prison capacity will enable us to transfer more prisoners to Nigeria, which will in turn free up prison places in the UK.”

The UK announced a £25m deal to build a prison in Jamaica in 2015 but the plan fell through following a dispute over funding.

Deals to send prisoners in UK back to their respective countries have also been made with Albania, Rwanda, Jamaica and Libya.