Watford have been promoted to the Premier League just nine months after they were relegated from the top flight.
The Hornets secured the second automatic promotion spot - following in Norwich City's footsteps - with a 1-0 victory over Millwall on Saturday afternoon.
Elsewhere in the Football League, Hull City were promoted to the Championship with a 2-1 victory at Lincoln City. At the other end of League One, a 1-0 defeat at Portsmouth sealed Bristol Rovers' fate, while Swindon were also relegated after their 5-0 thrashing by MK Dons
Ismaila Sarr was brought down in the box and converted a penalty in the 11th minute to grab his fourth goal in five matches and steer Xisco's men to victory.
With two games remaining in the season, Watford can still clinch the Championship title, although they will need Norwich to fail to win either of their two remaining games.
The Canaries beat Queens Park Rangers 3-1 on Saturday to maintain their five-point cushion at the table's summit.
Watford have been no strangers to managerial changes in recent years - sacking Javi Gracia, Quique Sanchez Flores and Nigel Pearson last term - and another mid-season appointment worked wonders this campaign.
Vladimir Ivic was sacked in December after a marginally underwhelming start to the season left the Hornets fifth in the table.
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Xisco was appointed as Ivic's replacement and brought about an upturn in form, leading the club on an impressive run of 10 victories in 11 games to pull clear of other automatic promotion hopefuls last month.
Sarr - the match-winner against Millwall - has been a standout performer throughout the season, top-scoring with 13 goals and laying on 10 assists for his teammates.
Watford also boast the best defensive record in the Championship having conceded just 28 times in 44 outings.
Attention now turns to the melee for the play-off spots, with Brentford, Bournemouth, Barnsley and Swansea currently occupying third to sixth in the table.
The Swans have an eight-point cushion over Reading in seventh.
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