Shetland is set to welcome the annual return of an almost 140-year-old fire festival.

Up Helly Aa, a 24-hour Viking festival, is expected to bring in thousands of participants and spectators to the streets of Lerwick on Tuesday night.

The first recorded event started in the early 1840s, when a group of bored young men were believed to have set fire to barrels of tar, creating drunken chaos in the town during the cold nights of January.

As the years went on, the festival became more refined with the town shaping the tradition into an actual event to celebrate the Norse history of the islanders.

It went through several incarnations until the late 1880s, when the festival was established in its current form, which is the largest fire festival in Europe.

Since then, it has expanded into a community wide family event, which is only cancelled for exceptional reasons. The last time the festival was cancelled was due to the Second World War, however, it was also postponed for one week in 1965 after the death of Winston Churchill.

It is lead by the Guizer Jarl, who has been preparing for this event for at least the last decade.

Stewart Jamieson will take on the role in 2018.

He follows in his father's footsteps, who was the Guizer Jarl in 1981.

A board of members select the Jarl and the current Jarl is elected up until 2033.

He and his Jarl Squad will lead the procession of 1000-odd men - no women are allowed to take part - with their own squads, through the streets of Lerwick.

The Jarl Squad, made up of friends and family, are the only group allowed to dress as Vikings. The other squads taking part will be in various states of fancy dress.

The main procession will take place in the evening, with thousands of torches set to be lit by the squads.

By 7.30pm, the town will plunge into complete darkness, apart from the light coming from the torches.

The procession will follow a galley - a Viking long boat - through the town towards its fiery end at the King George V playing field.

The route is due to be lined with spectators, which on a good night can reach 5000 easily, who will cheer on the squads as they pass by.

The galley will then be set down in its final resting place and set alight with the torches.

The evening will end with visits to locals halls, where each squad will provide entertainment for guests.

Every man has a duty (as the Up Helly Aa song says) to dance with at least one of the ladies in the hall, before taking yet another dram, which will be soaked up with vast quantities of mutton soup and bannocks.