The dramatic life and reign of Mary Queen of Scots is being remembered in a newly-released stamp collection.

A portrait of the monarch, who was executed more than 420 years ago, is featured on Royal Mail's new 81p stamp.

It forms part of a series depicting the seven Stewart kings and queens who ruled Scotland from 1406 until the Union of the Crowns with England in 1603.

The stamps, in 1st class, 62p and 81p denominations, went on sale today.

TV historian Neil Oliver unveiled the collection at Stirling Castle, the historic home of the Stewart monarchs.

He said: "The Stewart monarchy is a fascinating period of Scottish history with many dramatic characters and events.

"Mary Queen of Scots is obviously the most famous and colourful of the Stewart monarchs and it is wonderful to see her represented on a stamp.

"I'm delighted that Royal Mail is helping bring history to life through its series of stamps celebrating the history of Britain's kings and queens."

The series is the latest Royal Mail collection to feature the royal houses of the UK over the last 600 years.

The House of Stewart collection features contemporary portraits of each of the monarchs from the period - James I to VI and Mary.

It is the first time Mary, who was executed in 1587 at the age of 44, has appeared on a Royal Mail stamp.

Ian McKay, the group's Scottish affairs director, said: "Royal Mail has always made a great effort to celebrate diverse aspects of Scotland's history through its stamp editions and I am delighted that the Stewart monarchs and Mary Queen of Scots are being featured in this way.

"These stamps will be popular with anyone who is interested in Scottish history and I hope they can add to the good work done by places like Stirling Castle to preserve and pass on Scotland's heritage."

Julietta Edgar, head of special stamps at Royal Mail, said: "The House of Stewart marks the halfway point in this significant series of royal stamps, which takes in 600 years of British history and six royal houses."