The Dutchman returns to Amsterdam, his home city, to join our Champions League Group H opponents, who we face on 23 October. He originally joined the Blues from the Dutch champions in 2016.

Since his move to London, Castillo has represented the Netherlands up to Under-19 level and helped our Under-18s win a number of trophies, including back-to-back FA Youth Cups in 2017 and 2018.

In recent seasons, the 19-year-old has played most of his football for our development squad and Under-19s, helping the latter team to the UEFA Youth League final in each of the past two campaigns.

He will now get his first taste of senior football in the Eredivisie, with Ajax having won two and drawn one of their opening three league games of the season.