Royal Mail has unveiled a set of stamps featuring mythical creatures and fabled figures from UK folklore.

Designed by London-based artist Adam Simpson, the illustrations include the Loch Ness Monster, Cornish piskies, and Beowulf and Grendel.

The set of eight stamps and the stories each represents from different regions across the UK "demonstrate our rich mythological heritage", Simpson said.

They are available to pre-order from Thursday and go on sale on 27 March.

Other stamps in the Myths and Legends collection depict Blodeuwedd of Welsh mythology, Irish heroic figure Fionn mac Cumhaill, the spectral hound of East Anglia, Black Shuck, selkies and a grindylow.

Grindylows are sprites with long arms that lurk in rivers and ponds ready to snatch curious children in folklore from Lancashire and Yorkshire, while selkies are fabled creatures from Orkney and Shetland which shed their seal skins to take human form.

Simpson, whose previous work has been shortlisted for a British Design Award, said creating the stamps was a "privilege" and he was "really happy" to receive the commission.

"I think it's important to celebrate where these stories come from," he said. "Each one is associated with a region, and each one has its own identity, and together they demonstrate our rich mythological heritage."

Simpson previously designed a Royal Mail stamp to celebrate the Triathlon at the 2012 Olympic and Paralympic Games.

Illustrating stamps is challenging, he said, because "the composition needs to work at such a small scale".

To portray the fight between Beowulf and the monster Grendel, from the Anglo-Saxon poem Beowulf, he had to "figure out how to have two figures in a space that works on a small scale" and "wanted to suggest that Beowulf defeats Grendel by tearing off his arm without the image becoming disturbing".

Simpson said the project became a "real labour of love" and took more than a year to complete, with the illustrations evolving over time.

"It gave me the chance to be fully immersed in the world of these myths and legends. I hope that the stamps either start conversations or invite people to investigate the stories if they're not familiar with them."

David Gold, director of external affairs and policy at Royal Mail, said: "For some parts of the UK, local myths and legends are as much a part of their identity as the local landmarks and architecture.

"These beautifully illustrated stamps celebrate a fascinating aspect of British culture and custom."

The Royal Mail's Special Stamp programme commemorates anniversaries and aspects of UK history and culture, with the first commemorative stamp issued in 1924 to mark the opening of the British Empire Exhibition.

Previous collections have celebrated the diversity of the UK's wildlife, The Vicar of Dibley, and Paddington Bear.