Last season, the 21-year-old scored 13 goals in 38 La Liga appearances, including nine in the final eight league games.

He is the Blues’ second summer addition, following the £52 million transfer for RB Leipzig forward Christopher Nkunku.

“He is a young player with big potential,” remarked co-sporting directors Laurence Stewart and Paul Winstanley.

“We believe he is ready for this next step in his career and look forward to him working with our new head coach, Mauricio Pochettino, and his Chelsea team-mates.”

The sum was not disclosed by the two clubs, but it has been widely speculated that Chelsea will pay £32 million for Jackson.

Pochettino is restructuring Chelsea’s team, with a number of high-profile departures completed in the last week – and more due to come.

Arsenal have signed Germany attacker Kai Havertz for £65 million, while Manchester City have signed Croatia midfielder Mateo Kovacic for an initial £25 million.

Edouard Mendy and Kalidou Koulibaly, both of Jackson’s compatriots, have signed Saudi teams, while N’Golo Kante has agreed to join Saudi champions Al-Ittihad.

Winger Hakim Ziyech has also been linked with a move to the Saudi Pro League, while English midfielder Ruben Loftus-Cheek signed a contract with AC Milan on Friday.

What state is Chelsea in as Mauricio Pochettino takes over?
Bournemouth agreed to pay £20.3 million for Jackson in January, when he had three goals in 24 games in all competitions, but the deal fell through after his medical.

Jackson rejoined Villarreal in March and went on to win the La Liga player of the month award for May, assisting his team to fifth place and qualification for the Europa League.

Earlier in the season, he represented Senegal at the World Cup, making his debut against the Netherlands in the group stage.

Jackson earned two further caps in June, assisting in an Africa Cup of Nations qualifying match against Benin and a 4-2 friendly victory over Brazil in Lisbon, Portugal.