Lamb, who played 32 NRL games for Newcastle and was their rookie of the year in 2017, signed a two-year deal with the Roosters at the end of last season.

The 22-year-old playmaker was hoping he would be groomed to replace retiring champion Cooper Cronk but found himself surplus to requirements at Bondi Junction.

His only top-grade appearance was in round 11, coincidently against the Knights, and the Roosters copped a 38-12 hammering.

Since then the former Australian Schoolboys representative has been biding his time in NSW Cup, but news that the Roosters had signed Cronulla half Kyle Flanagan prompted Lamb to explore alternative employment.

He has signed with London until the end of the Super League season and will link with former Wests Rosella junior Yates, who played 25 NRL games for the Knights in 2017 and 2018.

Lamb told the Broncos' website: "I'm really excited to be coming over and having a crack. It's going to be awesome playing with Yatesy again. I can't wait."

Broncos coach Danny Ward said injuries and suspension had forced the club to strengthen its scrumbase options.

"Brock is a quality young halfback who we hope will give the squad a boost going into the final phase of the season," he said.

"He came with some decent raps from our people in Oz and is a former teammate of Yatesy, so I am sure he will fit right in."

London chairman David Hughes said: "I am delighted the club have been able to get the deal for Brock over the line as it is a big signing for us here in London. He comes with a NRL pedigree and I am sure our fans will be excited to see him play in this last part of the Super league season."

Lamb will arrive in the Old Dart to boost a London side struggling to avoid relegation from Super League.

The Broncos are last in the 12-team Super League, although they are only one win off eighth position. The team that finishes bottom is relegated to the 14-team second-tier Championship.

In their most recent outing, the Broncos upset competition leaders St Helens 32-12.

London have six games remaining, starting with Salford at home on Sunday.

Yates has been a revelation since arriving in the Old Dart and has made the second-most tackles in the league, 931 in 23 games.

Meanwhile, South Sydney prop George Burgess has at most four games left in the NRL after announcing he will join English Super League club Wigan at season's end.

The England Test prop has signed a three-year deal with the Warriors, in a move that will split him from his brothers Sam and twin Tom.

Burgess had wanted to stay in the NRL, but his asking price took a beating after he was suspended for nine games for his eye gouge on Tigers hooker Robbie Farah.

He will be available for the first week of the finals.

Burgess has played 147 NRL games since his debut for the Rabbitohs in 2012, including their 2014 premiership win, as well as 15 Tests for his country.