The city ladies needed to win their final two matches against nearest challengers Leicester Falcons and Norwich Devils at Bretton Park, the home of the Peterborough Lions rugby union club to finish top.
And a tense 6-0 win over Leicester followed by a much more convincing 35-6 win over Norwich led to great celebrations in the Royals camp.
The Leicester game was key to the outcome as they and the Royals started the day level on points.
And it turned into a defensive slugfest with neither team wanting to make a mistake with so much on the line.
Defensive captain Tanya Dales made the decisive play though with an interception which led to a touchdown and what turned out to be the only points of the game.
Although they struggled offensively, the Royals were outstanding in defence and picked up three more interceptions before the final whistle.
It was more straightforward against Norwich even though the Devils scored first with a close range touchdown as Royals started slowly.
The introduction of veteran quarterback Fabiola Kaiser turned the game in Royals favour. Her cool head settled the rest of the team down.
Running back Jade Heales levelled the scores before the break after breaking a couple tackles with further touchdowns arriving from Michelle Barkney, Ruth Archie, Sai Akhtar and Souzette Mutombo as Royals strolled to victory.
Wide receiver Akhtar caught a pass from quarterback Izzy Gibbs for the first ‘all-rookie’ touchdown of the season for Royals.
Mutombo scored after recovering a Devils’ fumble close to the end zone.
**The Peterborough Royals are always recruiting. Visit www.peterboroughroyals.co.uk for further information.