Grouville profited from a goalkeeping error and the ball twice sticking in puddles to score their first three goals on a wet and muddy Le Boulivot surface.
After St Brelade pulled a goal back with a fine strike from substitute Ollie Nightingale, the hosts finished of with two fine goals, the first from Peter Warrell and then Hughes’ stunner.
Toni Cardoso notched a brace after Chris Carter had nodded Grouville ahead.
The Portuguese Club of Jersey moved into second place in Division II, from a game played more over Jersey Nomads, following a 5-0 win away to St Lawrence.
Carlos Ferreira hit a brace, taking his total to seven in three games, while Miguel Perreira, Freddie Mendes and Flavio Olim added singles.
Nomads will have to win at leaders St Ouen on Wednesday night to regain second place.
Luke Heynes and Davey Reid were on target as fourth-placed Magpies won 2-0 at the Airport against St Martin/SCF.
St Clement moved up one place to eighth after winning 3-2 at home against Sporting Academics.
Matt Scriven (two) and Paul Walton notched for the Saints and Paul McLaughlin and junior Ben Gallichan for the Accies.
Junior Ryan Le Cornu hit a hat-trick in St Peter’s 5-1 home win against St Paul’s in Division I Reserves.
Darren Freeman and Mike Reed were also on target for the divisional leaders.
Junior Brett Willoughby replied.
St Ouen moved above Jersey Wanderers and St Paul’s at the bottom after they came from a goal behind at La Hague Manor to defeat First Tower 4-1.
Martin Sansom, Giles Johnstone-Scott, Dave Evans and Andy De Carteret registered for St Ouen and Wayne Shales for Tower.
Magpies maintained their four-point advantage at the top of Division II Reserves following a goal-less draw against Portuguese Club at Les Quennevais, the Portuguese Club’s third consecutive 0-0 score line.
Junior Josh Hinds and Jon Leonard netted for St Brelade and Jersey Nomads respectively in a 1-1 draw at St Brelade.
St John and St Clement also took a point apiece after sharing four goals at St John.
Tom Greechan and Jayson Lee were on the mark for the hosts and Martin Godfray and Kevin Cassin for the visitors.
Sporting Academics lost ground in the title race after they were beaten 4-3 by Beeches Old Boys at Les Quennevais.
Hamlyn Moon (two), Paul Skinner and Guy de Carteret scored for the winners and Ged Horgan, Simon Davies and Justin Spencer-Burrows for the losers.
Grouville took the Division C title after winning 6-0 at home to St Ouen.
The champions are also now just three games away from winning back-to-back Division C league and cup doubles unbeaten! Micky Kirk and Jason Byrne scored two each and Paul Cilia and Karl Stoodley one each.
Jon Rabey hit second-placed St Peter’s consolation as they went down 4-1 at home against Rozel Rovers.
Among the goals for the visitors were Sean Anderton (two) and Tony Amorin.
Jersey Wanderers beat St Lawrence 6-0 at the Hockey Club.
Jon Thwaites and Colin Jones bagged doubles and Alan Yates and Scott Young singles.
Junior Josh Hinds and Ged Horgan both grabbed their second goals of the day as St Brelade and Sporting Academics shared four goals at St Brelade.
Carlton McKain and Sam Bailey were also on target for the hosts and visitors respectively.
Jeremie Cup final: Guernsey Northerners 1, Trinity 2.
WJ Collins Memorial Trophy final: Guernsey Belgrave Wanderers v Jersey Wanderers postponed.
Coca-Cola Combination Div I: Grouville 5, St Brelade 1.
Div II: Beeches Old Boys v St John pp; Magpies 2, St Martin/SCF 0; St Clement 3, Sporting Academics 2; St Lawrence 0, Portuguese Club 5.
Div I Res: First Tower 1, St Ouen 4; Rozel Rovers v Jersey Scottish pp; St Peter 5, St Paul’s 1.
Div II Res: Beeches Old Boys 4, Sporting Academics 3; Magpies 0, Portuguese Club 0; St Brelade 1, Jersey Nomads 1; St John 2, St Clement 2; St Martin/SCF v St Lawrence pp.
Div C: Grouville 6, St Ouen 0; Jersey Wanderers 6, St Lawrence 0; St Brelade 2, Sporting Academics 2; St Peter 1, Rozel Rovers 4.
Ladies’ Colin Welsh Trophy semi-finals: St Clement 1, St Peter 5; Jersey Wanderers 0, St John 5.
Lloyds TSB Junior League U18 Div II: St Martin/SCF 5, Grouville 1; St Clement 0, St Ouen 4.
U16 Div I: Jersey Scottish 7, St Paul’s 0.
Div II: St John scratched to St Ouen.
U13 girls white: Jersey Wanderers 2 (Shannon Renouf, Ashley Cummins), St Clement 4.