Gosport & Fareham hooker Joey Clark scored a try on his debut but it was not enough as his side went down 29-17 to Trojans in London south west two.
The visitors had the game won in the first half, establishing a 23-4 lead before the interval.
Clark and Wes Dugan scored tries in the second period, both converted by Ryan Thorne, but it proved too little, too late.
'It was very disappointing because a couple of basic errors cost us the game,' said director of rugby Jamie Daly.
'We missed tackles that let them in for two tries in the first half.
'We showed character, coming back in the second half but unfortunately it wasn't enough for us to win.'
Petersfield romped to a 41-0 win over Old Wimbledonians in London south west three at Penns Place.
In Hampshire one, United Services lost 20-0 to a powerful Andover outfit.
Fareham Heathens chalked up an impressive 18-14 home win over Romsey.
Southsea Nomads sit at the top of Hampshire two after beating Lytchett Minster 31-7 in their top-of-the-table clash.
The visitors were quick out of the blocks, scoring two tries in the opening 11 minutes.
Prop Chris Groves and back James Hardy crossed and Chris Smith added the conversions.
Scrum-half Damien Parker forced his way over just before the interval to give his side a 19-7 lead.
In the second period further tries from Dan Tyler and Oli Bowles, plus another Smith conversion, saw Nomads to a comfortable home success.
Other Results: Portsmouth II 18 Tottonians 33;
Portsmouth III 29 United Services Portsmouth 21.