Earlier, the leader sparked anger over calls for international sanctions on Zimbabwe to be eased.
About 50 people gathered outside the South African High Commission, waving banners saying “Zuma save Zimbabwe”.
In response, President Zuma walked up a red carpet at South Africa House before turning and waving to demonstrators.
During his three-day state visit, the leader suggested sanctions should be eased to help Zimbabwe “move forward”.
But campaigners accused him of appeasing Zimbabwean President Robert Mugabe and believe he should be doing more to ensure fresh elections are called in the country.
Gordon Brown has said Zimbabwe must show progress in key areas including democratic reforms before sanctions are lifted.
At the protest, one man wearing a Mugabe mask held aloft a sign saying “Zuma – have another wife on me”.
The 67-year-old leader is a polygamist – following a Zulu tradition – and has taken a third wife.
Zuma said Friday he had put his point across about the need to resolve the crisis in the struggling country. He said he wanted to move forward as quickly as possible on Zimbabwe and expected to visit to his neighbour very shortly as part of South Africa’s efforts to broker an end to the crisis.
“I think we have put our point across,” Zuma told reporters Friday. “I think everybody has been saying they need to think about what was said so that we can have a resolution of the Zimbabwe problem.”
“With regard to South Africa this issue is not just a theoretical issue. It is an issue that impacts on South Africa,” Zuma said.
As the Zimbabwean economy has collapsed, 3 million Zimbabweans have fled across the border into South Africa, placing that country’s social infrastructure under severe strain.
“I am convinced that the establishment of those three commissions has given a new indication to the Western world that the Zimbabwean issue is moving forward,” Zuma said.
“What therefore we need is a response to that — that here is a process moving forward,” Zuma said. “We want to move forward as quickly as possible.”
Rose Benton, co-ordinator of a weekly demonstration outside the Zimbabwean embassy, said: “The government of national unity isn’t going to work, Mugabe isn’t serious about making it work – he never has been. “What we need is Zuma to do something, ” she said.
This has been the third state visit to Britain by a South African president since the advent of full democracy in 1994.
Nelson Mandela came to the UK in 1996 and Thabo Mbeki in 2001.BBC/Reuters