Theresa May is to announce plans to boost Britain’s investment in Africa after Brexit, during her first trip to the continent as prime minister.
At a speech later, Mrs May will say she is “unashamed” about ensuring Britain also benefits from its aid spending.
And speaking on her way to Cape Town, she played down warnings from the chancellor about the economic damage a no-deal Brexit could cause.
She will also visit Nigeria and Kenya during the three-day trade mission.
The trip – which will see Mrs May meet the presidents of all three countries – aims to deepen economic and trade ties with growing African economies ahead of Britain leaving the EU in 2019.
Arriving in South Africa on Tuesday morning, Mrs May is expected to say she wants the UK to overtake the US to become the G7’s biggest investor in Africa by 2022.
She will announce an “ambitious new approach” to the UK’s aid spending in Africa, by using it to help British private sector companies invest on the continent.
Private sector investment is key to driving growth and “unleashing the entrepreneurial spirit” in Africa, she will say.
Mrs May is also expected to say that creating jobs on the continent – where many countries have young populations – is “in the world’s interest”.
It is the best way to tackle extremism, instability and migration to Europe, Mrs May will claim, adding that otherwise the environmental and economic impacts will reach every corner of the world.
BBC political correspondent Ben Wright said like other European leaders the PM saw “huge economic potential to tap” in Africa and was keen to support economic stability in the region in order to “stem the flow of migration”.
Talking to journalists on board RAF Voyager on Tuesday morning, Mrs May reiterated that she believed a no-deal Brexit was still better than a bad deal – adding no-deal “wouldn’t be the end of the world”.
Last week Chancellor Philip Hammond warned in a letter that a no-deal Brexit could damage the economy. The warning came hours after Brexit Secretary Dominic Raab sought to play down the risk of a no-deal as he issued guidance for businesses in that eventuality – describing the impact as a “potential short-term disruption”.
The prime minister, who will be accompanied by a 29-strong business delegation to the three Commonwealth countries, previously said the trip would be a “unique opportunity at a unique time for the UK”.
The PM’s diary
Tuesday – Mrs May will fly into Cape Town where she will meet young people, before delivering a keynote speech on trade and how UK private sector investment can be brought into Africa.
After a bilateral meeting with South African President Cyril Ramaphosa, she is expected to visit Robben Island, where Nelson Mandela was imprisoned.
Wednesday – Mrs May intends to meet Nigerian President Muhammadu Buhari in the capital Abuja before meeting victims of modern slavery in Lagos.
Thursday – In Kenya, Mrs May will meet president Uhuru Kenyatta before visiting British troops and a business school. A state dinner hosted by Mr Kenyatta will conclude the trip.
The UK’s overseas aid budget totalled £13.9bn in 2017, an increase of £555m in 2016.
UK direct investment in Africa was £42.7bn in 2016, compared to £44.3bn from the US, £38bn from France and £31bn from China, according to data from the United Nations Conference on Trade and Development.
Security issues will also feature on the PM’s agenda and she is expected to discuss the threat of Boko Haram in Nigeria, and the role of British troops based in Kenya who are helping countries fight al-Shabab militants in Somalia.
Mrs May’s visit to Nairobi will mark the first by a UK prime minister to Kenya since Margaret Thatcher in 1988.
It is also the first to Sub-Saharan Africa by a British leader since David Cameron in 2013 for Mr Mandela’s memorial service.
A Downing Street spokeswoman added: “The PM will use the visit to announce further support to tackle instability across the region, because nations can’t prosper without it.”
During her time in South Africa, Mrs May is also due to present a World War One relic – linked to one of the worst maritime disasters in English waters – to South African President Cyril Ramaphosa.
The SS Mendi sank off the Isle of Wight in 1917 killing more than 600 South Africans en route to the Western Front to support British troops.
The ship’s bell was given to BBC reporter Steve Humphrey in 2017 in a plastic bag at Swanage Pier, Dorset, after an anonymous phone call – and will now be handed back by Mrs May.