The campaign is calling on people to join its efforts to make it a day honouring Welsh hero Owain Glyndwr.

The date marks the anniversary of the day in 1400 when Glyndwr was proclaimed Prince of Wales and the decision was made to rise against English rule.

A few days later, a small Welsh army rallied to Glyndwr's banner and attacked the English garrison town of Ruthin.

Next year marks the 600th anniversary of the event, which started the War of Independence.

Sculptor Ieuan Rees at work on the slate monument to Glyndwr

Until now the day has been honoured by events like the raising of the Prince's banner at Caerdrewyn near Corwen, Denbighshire.

The campaigners want Glyndwr Day/Dydd Gwyl Owain Glyndwr to become a permanent public holiday.

Organisers said they were calling on "all Welsh patriots" to lobby to ensure the event is honoured as a public holiday.

Welsh Heritage is urging the National Assembly to back the campaign and formally recognise the date.

They also want to encourage the Welsh flag to be flown on the day, along with Glyndwr's banner and the Cross of St David.

Monument

Recently, rival groups planning to celebrate the anniversary have crossed swords over plans for a 16-foot slate monument to Glyndwr in Machynlleth, Powys, the site of the prince's parliament house.

The Owain Glyndwr Society - which counts Sian Phillips and Bryn Terfel among its patrons - commissioned the monument for the grounds of the town's Celtica exhibition centre.

The move annoyed the managers of the site of Glyndwr's parliament in the town and also another group in nearby Pennal, where Glyndwr held court. They claimed the Celtica site lacked the historical associations of their own locations.