The 26-year-old loose forward is delighted to be staying put.
“I’m stoked to be staying on with the Broncos. It’s a great bunch of boys here, and I’ve loved my time with the club so far, so to be able to stay on longer is awesome,” he told his club’s official website.
“I’ve really settled in London and in Ealing in particular. It’s a great base for the club, and we’re working really hard to grow the game in the south of England.
“The boys have worked really hard for each other throughout this season, and we’ve all seen what the results of that have been.
“I’m looking forward to doing the same next season, and hopefully improving as a side year on year.”
London coach Andrew Henderson is pleased with how the player continues to develop.
“Harro’s been fantastic for the team,” he said.
“He has performed consistently over the course of this season and I feel has really stepped up in the Super 8s and showcased his quality and ability.
“He is a great bloke who is highly respected and popular throughout the club. We are thrilled he’ll be around for another season.
“He’s an incredibly reliable and durable player, and plays 80 minutes most weeks on the edge comfortably.
“I gave Harro a leadership role this season as vice captain and feel the added responsibility has brought the best out of him, both on and off the field.
“He has grown into the role over the course of the season and has done a great job stepping up to the role of captain – when Wes was injured – to lead the boys.
“Harro has played a true part in establishing and defining the culture at this club, and is exactly the kind of person you want at the heart driving the standards.
“I’m very happy with how our recruitment is going ahead of next season, as we have added some real quality to an already strong squad.
“However, I’m more pleased that the majority of the current squad has been retained, once again maintaining stability and continuity within the playing group.”