has thanked Southampton for all their support over the past year after leaving to join in a £58million deal.
The 19-year-old has become the Blues’ eighth signing of another busy summer at Stamford Bridge and follows hot on the heels of the £115m acquisition of Moises Caicedo from Brighton.
Chelsea fought off competition from Liverpool to land the Belgium international, who confirmed his departure in an emotional message on Friday.
He wrote: ‘To Saints Fans. As I say goodbye, I want to say a big thank you for everything you have given me during my time here.
‘I’ve instantly felt the love from you all despite us not achieving our shared goals. I’ll never forget the belief the club and Saints all around the world showed me and I hope I was able to repay the faith you put in me.
‘I would especially like to thank all my teammates and all staff members within the club involved closely or not for putting your arms around me since the day I walked through the Staplewood Campus and for all the daily work and help behind the scenes making me become a better person, athlete and football player.
‘You have all played a massive part into making my integration into real professional football easier.
‘I will be forever grateful to you. For those reasons, this club will always remain close to my heart.
‘Good luck this season and I look forward to seeing the club marching back to the Premier League where it belongs very soon! Thank you Saints. Romeo.’
Lavia posted his message early on Friday morning and around an hour later the transfer was confirmed by Chelsea.
The youngster is in line to be part of Sunday’s squad to take on West Ham, with Chelsea having had until midday on Friday to register him for the clash.
Lavia, who came through the academy at Manchester City, attracted interest from a host of top Premier League sides following Southampton’s relegation.
Liverpool had initially balked at Saints’ asking price and had multiple bids rejected before Chelsea swooped in to agree a deal worth £58m.
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