2013122320140122Luanda, the capital of Angola, is currently the most expensive city in the world. Along the seafront, recently revamped at a cost of $350 million, Africa's most expensive one-bedroom apartment was snapped up for $9million, and a hamburger will set you back $30.

Yet forty years ago it was a war zone. Angola won its independence and hundreds of thousands of Portuguese colonialists fled in panic.

Now they're coming back and BBC Africa Editor Mary Harper finds out why. She meets some of the Portuguese who are leaving the economic crisis at home to cash in on Angola's oil-driven boom, and uncovers the tensions this reversal of fortunes is creating between the once-colonised and their former rulers. The migrant flood has been recent and rapid. In 2006, only 156 Portuguese emigrated to Angola. In 2012, there were 30,000.

Among the Portuguese returnees, is a scuba diving instructor from the Algarve, now earning double in Luanda, and a young family from Portugal raising their children as Angolans.

As well as providing jobs, and lucrative construction and engineering contracts, Angolans are also propping Portugal up by investing heavily on Portuguese soil - in the banking, energy and telecoms sectors. But just days before the Radio 4 team arrived in Luanda, the usually taciturn Angolan president, Jose Eduardo dos Santos, gave an outspoken speech, saying all was not well with Portuguese relations.

Producer: Eve Streeter

A Pier production for BBC Radio 4.