Thornensians won the Yorkshire Silver Trophy with an 18-13 victory over rivals Wetherby.
In doing so, Thorne officials say they are now the only club in the county to have won all four major trophies - the Yorkshire Cup, Yorkshire Shield, Yorkshire Silver Trophy and South Yorkshire Trophy.
Thornensians dominated Sunday’s final against the team that pipped them to Yorkshire Three title for long periods but struggled to convert that into points.
Wetherby took the lead with a converted try on 12 minutes but Robert Brown kicked penalties on 21 and 26 minutes to narrow the gap to 7-6.
Wetherby kicked a penalty on the half hour but Thorne centre Luke Marsden ran in for a try just before half time to give his side a narrow 11-10 lead.
A second penalty just after the re-start put Wetherby back in front at 13-11.
But left winger Oliver Cox raced over for a 55th minute try, which Brown converted, to put Thorne into the lead, and they held firm for the remaining 25 minutes.
Thornensians and Wetherby will both be playing in Yorkshire Two next season after winning promotion.