This was only the Trojans second league defeat of the season and a game in which they could have been crowned champions.
However, a slow start cost the Trojans dearly, meaning their large army of travelling supporters had to put their promotion celebrations on hold.
Leigh put Thornhill under pressure straight from the kick off and built up a 22-0 lead, leaving the visitors with a mountain to climb.
A high kick on the last tackle caught Thornhill out. With men up in support of the attack Tom Farrimond ran onto a pass to score. Scott O’Brien converted.
The next Miners attack saw Thornhill breath a collective sigh of relief when the referee disallowed a try for offside.
But still the hosts continued to torment Thornhill and were first held short of the try line in the corner but kept the ball alive to score through Joe Connor with O’Brien converting.
Miners then fluffed a penalty goal attempt before they again turned the screw. A break upfield was capped by a fine inside pass which found Scott O’Brien, who raced clear for a try which Craig Ashall converted.
Thornhill briefly lost the services of Jake Wilson when he had to leave the field due to a badly cut face.
Once play restarted Thornhill had another defensive lapse and hooker Tom Farrimond snuck over from close range for an unconverted try.
Despite now trailing by 22 points they demonstrated grit and entered what turnout out to be their best phase of the game.
A break started by Casey Johnson was supported by Danny Ratcliffe but the move broke down when Joel Gibson was felled by a high tackle.
Thornhill continued their mini revival with Danny Ratcliffe, Luke Haigh and Casey Johnson all at the thick of the action, while Zach Johnson was held up over the try line.
Thornhill’s endeavour finally paid off when man-of-the -match Danny Ratcliffe stepped through a gap and raced clear of the defence before passing inside to put the supporting Haigh away for a try which Joel Gibson converted.
Thornhill desperately looked to score again in the run up to half-time but the try they required never materialised and as the second half got underway they had a body blow.
Straight from the restart Leigh were held short of the try line but a swift play the ball resulted in Mick O’Boyle forcing his way over to score.
Craig Ashall added the conversion and it proved to be a game clinching moment for Leigh Miners.
Thornhill looked to have scored through Nick Mitchell but the referee ruled that there had been a knock on.
Jake Wilson was sin-binned for a dangerous tackle but this didn’t prevent Thornhill from putting up a fight as Danny Ratcliffe was held short of the line.
Liam Morley then broke clear and put George Woodcock over for in the corner.
Thornhill had Gibson sin binned when he prevented Miners from tacking a quick tap and Leigh used their extra man advantage and produced a good passing for winger Lee Gittins to score in the corner.
Thornhill battled to the end and Danny Ratcliffe broke with Haigh again in support to score the try. Woodcock converted.
Thornhill must now lift themselves from this defeat and once again go in search of one more league win which will secure promotion.