The prime ministers visited the Borough Markets on Monday after greeting a range of first responders, including Australian ambulance officers, and police.
"They didn't think of themselves but went to help those who they saw in need".
UK Prime Minister Theresa May greets Malcolm Turnbull outside 10 Downing Street.
"We stand shoulder to shoulder now, as we always have, in freedom's cause today, defying and defeating the Islamist terrorists that seek to do us harm, to seek to destroy our way of life and prevent us from living our way of life as we always have".
Speaking alongside Theresa May, having met for extensive discussions, Mr Turnbull said he would look to establish the arrangement as soon as the United Kingdom can "lawfully" do so after it has severed ties with Brussels.
Wearing fake suicide vests, all three attackers, Khuram Butt, 27, Rachid Redouane, 30, and Youssef Zaghba, 22, were shot and killed by police in a hail of bullets at the scene.
Ms May and Mr Turnbull also spoke to business owners in the food market, which is surrounded by restaurants, bars and cafes.
'They were very courageous men, very fearless men and women and I just want to thank them on behalf of all Australians.
The 41-year-old said: "They were really exposed but somehow they stayed safe, and there was a customer inside - we were lucky".
But others were more positive, relating their stories of how terrified people reacted. They also spoke to traders in the market, one of London's most popular visitor attractions.
Before heading home, Mr Turnbull will also have an audience with the Queen.
"This office will provide a collaboration space for the Naval Group and Lockheed Martin Australia to work closely with our Australian government partners to provide the best possible submarine fleet to provide protection for Australia's trade and assure the nation's maritime security", said Vince Di Pietro, CEO of Lockheed Martin Australia and New Zealand.
"They ran towards the danger while others were fleeing the danger".
"It was very moving to meet them".
Speaking to reporters after the leaders met to discuss security and trade, Mr Turnbull was asked how long it would take to secure a new trade deal after Brexit.
Mrs May said: "I am deeply grateful to Prime Minister Turnbull and the Australian people for the solidarity and support they have shown the UK". We are so close, and that trust is getting stronger all the time ...