The Bees were crowned Uhlsport United Counties League Premier Division South champions after a 2-2 draw on the final day of the season at Newport Pagnell last weekend.
They had already secured promotion to Step 4 for the first time in the club’s history.
And they wasted no time in adding a second piece to silverware to their trophy cabinet as they saw off league rivals Potton United 4-0 in the final of the Hinchingbrooke Cup at Yaxley on Wednesday night.
Nat Ansu was the hero for Harborough. He opened the scoring five minutes before half-time and then went on to complete a hat-trick before James Ireland rounded things off 10 minutes from full-time.
There’s now just one more job for Mitch Austin’s team to try to get through.
Tomorrow (Saturday), they entertain UCL Premier Division North title winners Long Eaton United in the Champions Cup (3pm kick-off) as they look to complete the season with a unique treble.