Malcolm Turnbull and Theresa May have met Australian ambulance officers and British police who responded to last month's terror attack in London.

The prime ministers visited Borough Market on Monday, with Mr Turnbull on behalf of Australians thanking the "very brave" police officers who tried to save people, including two young Australian women who died that night.

The pair visits stall holders at Borough Markets and thanks first responders. (AAP)

Theresa May and Malcolm Turnbull outside 10 Downing Street. (AAP)

The leaders, who have known each other since their Oxford University days, walked through the market, talking to stall holders about the devastating event.

As they stood just near where the terrorists were shot dead, some of the vendors described how terrified people reacted. "You've shown great resilience," Mr Turnbull said.

The Borough Market only recently reopened after the June 3 attack, in which eight people were killed and almost 50 wounded.

Three terrorists drove a van into pedestrians on London Bridge before abandoning it to run into the popular area, stabbing people with foot-long knives as they went.

The attackers killed South Australian nurse Kirsty Boden and Queenslander Sara Zelenak.

South Australian woman Kirsty Boden was killed in the June attack. (Supplied)

Queenslander Sara Zelenak was also killed in the June attack. (Supplied)

Ms May later welcomed Mr Turnbull to Downing Street for talks, including plans to work more closely together on national security matters.

Speaking in the White Room before the meeting, Mr Turnbull became emotional as he spoke of his earlier meeting with police who had tried to save Ms Zelenak, saying he had found it hard not to "burst into tears" as he heard what happened.

"They were very brave men, very brave men and women and I just want to thank them on behalf of all Australians.

"It was a very moving visit ... and I want to say how much we admire the outstanding response of your police arriving on the scene so quickly, dealing with the terrorists so effectively and decisively," Mr Turnbull said.

"They ran towards the danger while others were fleeing it."

Ms May praised Ms Boden who "rushed to the scene" to help others only to lose her own life.

Malcolm Turnbull received an intelligence and security briefing from top British officials. (AAP)

"They didn't think of themselves but went to help those who they saw in need."

Mr Turnbull earlier received an intelligence and security briefing from top British officials.

The prime minister and Metropolitan Police commissioner Cressida Dick - Scotland Yard's first female boss - discussed terrorist attacks in the UK and Melbourne as well as the June 14 Grenfell Tower fire.

They talked about better ways to protect crowded places and the challenges of cyber-terrorism and encryption, which was a focus of talks at the G20 summit in Hamburg.

The leaders discussed the "opportunities" raised by Britain's exit from the European Union, including a potential free trade deal with Australia once Brexit occurs.

"Discussions on an ambitious and comprehensive bilateral trade deal with Australia remain a priority for the UK," Mrs May is expected to say.

The UK cannot legally negotiate trade agreements until after exiting the European Union but Mr Turnbull wants to move as quickly as possible when that happens.

Before heading home, Mr Turnbull will also have an audience with the Queen.