Portsmouth suffered an agonising 29-27 defeat against Old Tiffinians in their top of the table London Three South West contest at Rugby Camp.
In a dramatic finish, the home side were leading 12 minutes into stoppage time at the end of the game.
With all eyes on the clock, Portsmouth conceded a penalty wide out on their twenty-two.
To the horror of the hosts, the visiting kicker held his nerve and sent the ball between the posts with the final kick.
Senior coach Neil McRoberts admitted it was a difficult defeat to take.
'It was all very frustrating at the end,' said McRoberts.
'We had at least three opportunities to get the ball off the pitch and didn't take them.
'Then at the end we get a penalty but opt for a scrummage and eventually turned the ball over.
'That gifted Old Tiffinians the chance to win it.
I can't fault our effort and physicality but it was a game that we should have won.
'We got ourselves into a position to see the game out but didn't do it.'
The game between the top two sides proved to be a close fought encounter from start to finish.
It was a great advert for London South West Three rugby with the lead changing hands four times.
Portsmouth struck the first blow with a try after just four minutes.
Full back Mark Ovens made a terrific break to score midway between the posts and the touchline with Tom Hopkins adding the conversion.
The visitors hit back with a penalty before Portsmouth struck with their second try.
Again Ovens was pivotal, collecting an Old Tiffinians kick ahead and making good ground before putting winger Hopkins in wide out.
Though the visitors reduced the lead to 12-11, tries from centre Robert Lamberton and winger Noah Cannon gave the home side a 24-14 lead at half-time.
In the second period Portsmouth had captain Daz Leggett yellow carded for a high tackle.
Old Tiffinians exploited this to take a 26-24 lead but the initiative swung back to Portsmouth two minutes from the end.
Lamberton knocked over a penalty to give the hosts a one-point lead.
But just when it looked as though they had done enough, Portsmouth had the win cruelly snatched away from them.
'It was a bitter pill to swallow,' said McRoberts.
'On a positive note, we picked up two bonus points and didn't lose too much ground at the top.
‘It is still very early in the season and this is just one game.'