In what was described by manager Andy Landesberg as a "huge performance" Lions won away at their promotion rivals with a solitary early goal from Adam Bolle.
In difficult conditions, Lions had to battle against the weather plus a very strong opponent in Baldock and from back to front performed manfully.
Lions defensive unit, with James Harpin in goal, was particularly strong, while Jake Rinsler was on top form, as well as Nick Landesberg and Tom Smith outstanding under plenty of pressure from the home team.
The visitors nicked the only goal after 15 minutes when good play between Jake Furman and Liron Mannie saw the latter whip in a super cross for Bolle to head in his 20th goal in just 13 games since re-joining from Aveley.
While Lions created more chances after this, defending this precious lead was achieved with a huge amount of work from all concerned and a deserved final – the team’s 4th in 3 years – now awaits.
Lions will face runaway league leaders Southall or Ampthill Town for the cup.
LIONS: James Harpin, Jake Rinsler, Adam Myeroff, Nick Landesberg, Tom Smith, Adam Lipman, Jake Furman, Jordan Marks, Austin Lipman, Adam Bolle, Liron Mannie. Subs: Sam Hamerton, Adam Arnold
GOAL: Bolle 15
Man-of-the-match: Tom Smith