Portsmouth got the city bragging rights with an 18-12 derby win against United Services at Burnaby Road.
With both teams pushing at the top of London three south west it was always going to be a hard-fought affair.
Neil McRoberts put success down to the way Portsmouth dealt with the big home pack of US forwards.
The powerful contest saw the visitors stand strong.
Portsmouth’s head coach said: ‘We fronted up and showed great physicality.
‘Over the whole 80 minutes I feel our win was well deserved.
‘We knew Services would come at us from the start and our defence in the opening 10 minutes was magnificent.
‘During that period we managed to contain them.
‘It was a good hard honest game of rugby.
‘Second-row forward Louis Bristow had his best game for us and prop forward Ben Lanigan at prop was immense.
‘Apart from the tries we scored three or four other chances went begging.’
Scrum-half Chris Morgan kicked an early penalty to put the visitors ahead.
Services hit back and a good touch-kick pinned Portsmouth back into their own twenty-two.
From a five-metre scrum the big home pack drove over for the try which gave them a 7-5 lead after 17 minutes.
A second Morgan penalty restored Portsmouth's lead who added a try before half-time.
With United Services under pressure prop forward Finn Parry picked up and dived over from close-range.
At the start of the second half Services found it difficult spending any long periods of time in the visitor's half.
With 10 minutes remaining Portsmouth stretched their lead through a Sully CauCau try converted by Morgan.
This only seemed to spur Services on and refusing to give up they pulled back to within seven points with a converted try.
McRoberts praised the home side for not letting the match get away from them and he was also impressed with the way his team closed the door.
He added: ‘To their credit Services came back at us and deserved their bonus point.
‘The way we managed to close the game out in the final few minutes was pleasing.
‘It is an excellent result for us and sets things up nicely for the important period leading up to Christmas.’
The situation at the top end of the league remains very tight.
Just six points separate the top four teams.
Portsmouth remain in third place but United Services slip to fourth spot.
Services player coach Rich Neil felt his team failed to perform at their best.
He said: ‘It wasn't much of a spectacle and the game never really took off..
‘The game was very stop-start in nature.
‘We didn't reach our usual standards and our basic handling skills let us down.
‘It took us until the final 10 minutes to really get going.’
Meanwhile, Petersfield are still without a win following a 35-7 defeat at Old Tiffinians.