A tiny island in the corner of a distant ocean will vote next Sunday to become a French département or county – defying a separatist trend in other fragments of France scattered around the globe.

Mayotte in the Indian Ocean, population 180,000 and roughly the size of the Isle of Wight, is confidently expected to vote to become the 101st département of France in a long-awaited referendum. Despite the angry opposition of the African Union and the nearby Comoros, the islanders have long insisted that they want to retain, and even solidify, their Frenchness.

They are expected to vote overwhelmingly to end their present vague status as a French “overseas collectivity” and agree to become a fully fledged overseas département – legally as much a part of France as Paris or the Pas de Calais.

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When the new status takes effect in 2011, the overwhelmingly Sunni Muslim people of the one large and one small island in Mayotte will have to come in line with the French legal code. Among other things, they will have to give up Islamic courts, polygamy and child marriages. They will qualify gradually for French social benefits over 25 years.

The vote in Mayotte may appear to be a historical anachronism. The African Union has long supported the sovereignty claim of the nearby Comoros Islands, which were once part of a single French colony with Mayotte. Some other parts of foreign oceans which are forever France, such as Guadeloupe and Martinique in the Caribbean and Réunion in the Indian Ocean, have increasingly powerful separatist movements. All three have seen serious, social unrest in recent weeks in which protesters have complained about low wages and the high cost of living. Nouvelle Calédonie, the French territory in the Pacific, has begun a process which is expected to lead to full independence some time after 2014.

The people of Mayotte – “les Mahorais” – have already voted four times since 1974 to remain part of France. All political parties in the island have recommended a “oui” vote in Sunday’s referendum. The Mahorais fear domination by the larger population of the Comoros islands and hope to develop their economy – based on manioc (cassava), bananas and tourism – more rapidly as part of France. Unemployment in Mayotte is around 29 per cent but has been falling in recent years.

Under the terms offered by next week’s referendum, the islanders will qualify for somewhat increased social benefits as soon as they become a French département in 2011. However, full benefits would not be paid until 2031 or 2036.