Diamonds suffered a 2-0 defeat at title-chasing Egham Town but, with St Ives Town winning 2-0 at Aylesbury, it means Andy Peaks’ side are now assured of a top-five finish as they seek a second successive promotion.
It has also been confirmed that Diamonds will be away in the play-off semi-final, which is due to be played next Tuesday night and they will travel to one of Kings Langley, Egham or Royston Town who are battling it out for the sole automatic promotion slot.
Diamonds started brightly at Egham with Jon Stevenson having a close-range volley blocked before Claudiu Hoban forced the home goalkeeper into a good save after cutting in from the right.
Matt Finlay was called into action at the other end as he produced a fine stop from Elliot Carey’s deflected effort.
But Diamonds continued to create openings as Lewis Leslie shot wide before Stevenson had another curling effort saved.
Stevenson departed through injury before the break and the hosts took the lead four minutes after the restart.
Liam Dolman was penalised for a foul in the area and Bajram Pashal stepped to beat Finlay from the spot.
Egham went on to dominate proceedings from there and Brendan Matthew flicked a header just wide while Dolman was off target in an opening for Diamonds late on.
But Egham wrapped up the points deep into stoppage-time when Matthew was chopped down by Jack Ashton and he picked himself up to send Finlay the wrong way from the spot.
However, news of St Ives’ victory had already been confirmed before the full-time whistle blew, meaning Diamonds knew they had secured a play-off position.
They round off the regular season with a home clash against Godalming Town at the Dog & Duck on Saturday.