Newlove has not always been at his best this season and he did not add to his tally of 14 tries last night. But he did provide the pass for all five scored by his wing partner Sullivan as Saints overcame a wonderful London fightback to finally knock them out of contention for the Super League play-offs.
Sullivan, taking his total for the year to 19 by equalling the Super League record for tries in a match, finished superbly, but he would acknowledge that the service provided by Newlove was sumptuous.
Without the potency of Saint's left-wing combination, this would have been a very different game, because in other respects a London team desperate for a win gave as good as it got.
After both sides had scored early tries through Tommy Martyn and, on his last appearance at The Stoop, Mark Carroll, however, Newlove and Sullivan began their demolition of the Broncos' hopes.
The dust had just settled after a mass punch-up which saw Paul Davidson and Robbie Beazley sin-binned when Newlove's glorious break set up Sullivan for his first when the centre could easily have scored himself.
Sean Long's clever pass sent in Paul Sculthorpe and another Newlove run again released Sullivan as Saints seemed to take firm control before half-time.
Whatever their other shortcomings this season, London did not lack tenacity last night and they came back in extraordinary fashion after the break, despite absence of Shaun Edwards, withdrawn by his coach, Tony Currie, as a tactical measure.
Beazley's well disguised pass sent Grant Young crashing over and Glen Air ghosted through a gap.
With Chris Ryan converting both tries, London were suddenly only three points behind and they took the lead for the first time when Bart Williams capitalised on the good progress made by Ryan and Matt Salter to go over from close range.
The receding prospect of the Bronco's pipping Bradford for the final play-off place was once more hauled back on to centre stage, but that was merely the cue for Newlove and Sullivan to step up their destructive double act.
A flowing five-man move ended with the Welsh wing man completing his hat-trick and two more in the last five minutes left London ruing the sheer quality of his contribution and that of his provider.
"Our season was killed off by two players who were absolutely world-class," said Currie. "I'd give my right hand to have them on the left-hand side of my team."
London Broncos: Toshack; Smyth, Timu, Ryan, Cotton; Air, Edwards; Young, Beazley, Carroll, Retchless, Millard, Gill. Substitutes used: Stencer, Salter, Dunford, Williams.
St Helens: Atcheson; C Smith, D Smith, Newlove, Sullivan; Martyn, Long; Goldspink, Cunningham, O'Neill, Perelini, Davidson, Sculthorpe. Substitutes used: Wellens, Matautia, Anderson, Stewart.
Referee: S Cummings (Widnes).