A late penalty condemned Portsmouth to a 12-10 London three south west defeat at Warlingham on Saturday.
The visitors led 10-9 with six minutes remaining but an infringement allowed the hosts to regain the lead.
Portsmouth director of rugby Jim Pearce admitted it was a disappointing day.
‘It was a day when we were not quite there,’ he said.
‘We were 10 minutes late arriving and that put our pre-match schedule out.
‘That had a knock-on effect in the first half.
‘In the second half, we took more control and had the chance to win the game.
‘We played some reasonable rugby in difficult conditions.
‘Their goal-kicker, however, proved the difference.
‘Warlingham defended well and didn’t give us many opportunities.
‘It is important we draw a line under it and are ready to go again.’
The hosts led by a single penalty at the halfway mark and quickly added two more at the start of the second period.
Portsmouth scored their try in the 49th minute after Mark Ovens ran a clearance kick back and forced a five-metre scrum, from which Rhys Bowen picked up and forced his way over.
Simon Morgan added the conversion and later knocked over a penalty but it was not enough.
Unbeaten Hampshire one leaders United Services made it 15 straight wins with a 31-7 success at Ventnor.
In Hampshire two, Southsea Nomads lost 36-13 at leaders Romsey.
The Nomads, whose forwards were on top for a lot of the game, were still in with a chance eight minutes from the end.
But the promotion favourites made their quality count with some sharp running by the backs.
Nomads’ stand-in captain Joe Beale said: ‘The boggy conditions did not allow us to unleash our full attacking potential.
‘Everyone defended well – forcing Romsey to try to attack us out wide.
‘It is a privilege to lead an ever-improving team.
‘Every week seems to highlight a different area in our game where we have done better.
‘It is an exciting time to be involved with the side.’