Tydd St Mary booked their place in the ChromaSport & Trophies Intermediate Shield final with a 1-0 victory at Spalding Town.
After beating Division One side Long Sutton Athletic last week to reach the Spalding Inter Services Cup final, they claimed another giant-killing act.
Town had the first chance on seven minutes when Saints keeper David Cooper pulled off a top-class save.
Tydd took control after 27 minutes when Will Kirkham floated a free-kick into the box and Daniel Piccaver headed over keeper Brendan Taylor.
Tydd almost scored their second when a near-post corner by Nick Reims was met by the head of Darren Rawthorn but Taylor pulled off a great save.
Five minutes before half-time, Cooper was called into action again and pulled off another fine save to keep it at 1-0.
Tim Lowe had an isolated game up front as the Saints were pegged back deeper by a fired-up Spalding Town but he almost made it 2-0 on 54 minutes when he narrowly fired wide.
With the Tydd back four superbly marshalled by man of the match Piccaver, Spalding Town struggled to get any shots on target and resorted to long balls into the box which were cancelled out every time.
Following a goalmouth scramble Town should have equalised when former Tydd skipper Gary Booth blazed over from two yards out when it was more difficult to miss.
Piccaver cleared a shot off the line and Jason Powley blocked another effort.
The Saints held on for a deserved win and progress to the final against Division Two side Whittlesey Athletic A.
Manager Carl Wilson said: “This was a great team performance by the lads.
“Every player to a man stood up strong and played their hearts out.
“I am very proud to be a small part of this great squad of players.”