Frank Lampard was appointed Chelsea head coach on Thursday, confirming a dramatic return for one of the club's greatest ever players.
Lampard has signed a three-year contract with the Premier League club, where he spent 13 years and became the team's all-time leading scorer with 211 goals.
The former England midfielder succeeds Maurizio Sarri after just one season in management, having led Derby County to the Championship play-off final in May, when they were beaten by Aston Villa.
"I am immensely proud to be returning to Chelsea as head coach," Lampard said in a club statement.
"Everyone knows my love for this club and the history we have shared, however, my sole focus is on the job in hand and preparing for the season ahead.
"I am here to work hard, bring further success to the club and I cannot wait to get started."
Lampard made 648 appearances for Chelsea, winning three Premier League titles, four FA Cups and two League Cups, as well as the Europa League and the Champions League.
Chelsea said Lampard had a "fantastic relationship" with the club's supporters and he will certainly lift the mood after a fractious season under Sarri.
Despite finishing third in the Premier League and winning the Europa League, Sarri was criticised for his eccentric approach and rigid style of play.
"Frank possesses fantastic knowledge and understanding of the club and last season, he demonstrated he is one of the most talented young coaches in the game," said Chelsea director Marina Granovskaia.
"After 13 years with us as a player, where he became a club legend and our record goalscorer, we believe this is the perfect time for him to return and are delighted he has done so.
"We will do everything we can to ensure he has all the support required to be a huge success."
Derby granted Chelsea permission to speak to Lampard after reportedly agreeing a compensation package of around £4 million ($5 million) to release him from the remaining two years on his contract with the Championship club.
Chelsea are unlikely to be able to make any new signings this summer as they are serving a two-window transfer ban from FIFA.
And their best player of recent times has also departed after Eden Hazard completed a 100 million euro ($114 million) move to Real Madrid.
Lampard is therefore expected to oversee a sea change in Chelsea's policy, concentrated on giving more opportunities to products from the club's youth academy.
His assistant Jody Morris has extensive knowledge of the Chelsea youth system having been a key figure at the club's academy prior to joining Lampard at Derby last summer.
However, they face a baptism of fire with their first two competitive games in charge featuring a trip to Manchester United on the opening weekend of the Premier League season followed by the UEFA Super Cup against European champions Liverpool.
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