Participants will dress in full norse costume

The chief viking - known as the Guizer Jarl - and his squad of 50 men escort a 30ft galley through the town to the harbour.

This year's Guizer Jarl is Michael Groat, a 38-year-old mechanical supervisor from Lerwick, who has been growing a beard to help him look like a genuine norseman.

The main part of the festival begins after dark when about 900 men bearing blazing torches gather for a procession through the streets.

Accompanied by a brass band, the procession makes its way to the playing fields.

Participants then fling their torches into the longship and sing traditional songs as they watch it disappear in flames.

Shetland's villages hold their own fire festivals in the first months of every year.

Lerwick school pupils are staging a small-scale version of the festival before the main event begins.