Now, pressure appears to be growing on the organisers of Up Helly Aa to admit women into the main procession that accompanies the chief - or Guizer Jarl - as he makes the journey to his burning galley boat.

Calls to admit women to the procession in recent years have broadly been met with weary derision from those who are proud of the Lerwick tradition that has become a popular promotional tool for tourism to the islands, with the jarl and his supporters attending events in Edinburgh and New York in recent years.

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Pressure is growing on the organisers of Up Helly Aa to admit women into the main procession picture: PA

Yesterday morning a group called Reclaim the Raven, which references both the Lerwick crest and Norse mythology, pinned an alternative message to the Market Cross in the town at 5am, around an hour before the Guizer Jarl traditionally pins up his proclamation in the same spot.

A statement added: "We hope the Up Helly Aa committee would show these and engage with everyone in bringing a bright and inclusive future to this festival that is loved around the globe.

"No one wishes to see Up Helly Aa become better known for the exclusion of woman and girls than for being the biggest and best fire festival in Europe."

A web cam apparently captured two men taking down the Reclaim the Raven message and putting it in the back of a van around 8am yesterday.

Zelda Pennington, of the group, said attempts to get women into the main procession were 'stonewalled' by the Up Helly Aa committee. Another group, Up Helly Aa for Aa, is also active in campaigning for the inclusion of women in the event.

She said: "Our main concerns are that Up Helly Aa also has a junior festival in the schools so children are getting exposed to this exclusion of girls at a very young age, at a primary age.

"This year they couldn't get enough boys from Lerwick to take part so instead of opening it up to girls from Lerwick, they opened it up to boys from all over the islands."

Other Up Helly Aa festivals in Shetland include women and girls in the event.

She said: "Some festivals have made a choice of being inclusive. Some are concerned that these ideas of gender exclusion are being re-imported into their areas.

"We are also concerned how it impacts on the community and the values within that community."

Up Helly Aa first started in the 1820s and was loosely tied into the old celebration of Yule. It latterly evolved into a celebration of Shetland's Viking heritage.

In 2015, Lesley Simpson from Maywick became Shetland's first ever female Guizer Jarl when she represented Bigton and Levenwick for the South Mainland Up Helly Aa.

The Lerwick Up Helly Aa is referred to as 'transvestite Tuesday' by some given some of the jarl squad dress up as women for the event.

Shetland Isles Council, which gives no funding to Up Helly Aa, puts on a civic reception for the Guizer Jarl every year with the day after the event a public holiday in Lerwick.

Malcolm Bell, Convener of Shetland Islands Council: “Lerwick Up Helly Aa continues to be an event which draws large numbers of people to Shetland and is widely enjoyed and supported in the community. I recognise that there are some strongly held views on both sides of this debate. Lerwick Up Helly Aa is a privately run event, run by the community, and the format is therefore a matter for their organising committee.”

The Up Helly Aa was contacted yesterday (Tuesday) but no one was available for comment.

Pressure builds to let women march as Vikings in Shetland's Up Helly Aa festival