Kgalema Motlanthe, a respected former guerrilla and union leader, on Thursday became South Africa’s third black president and vowed to restore order amid the biggest upheaval in the country’s politics since the end of white rule 14 years ago.

Thunderous applause by the MPs who installed him as caretaker president temporarily drowned out the clamour among South Africans and investors unnerved by last weekend’s ousting of Thabo Mbeki as president, the successor to Nelson Mandela, by his enemies within the ruling African National Congress.