The Thistle Installation service, is usually held in the Chapel of the Order of the Thistle in St Giles Cathedral every other year. The Order of the Thistle is one of the most exclusive honours bestowed upon an individual by the Queen (the English equivalent is the Order of the Garter), and as such makes a colourful heraldic spectacle during Royal Week (aka Holyrood Week) in Edinburgh.
Members of the public must apply for tickets in advance (see link above).
On the day, members of the Guard of Honour (found by Royal Company of Archers), accompanied by the Band of the Royal Regiment of Scotland, take up position in Parliament Square (outside St Giles).
When the Queen and the Duke of Edinburgh arrive at Parliament Square, the Chancellor of the Thistle, the Dean of the Thistle and the Secretary of the Thistle escort the Queen to the Signet Library, where the Knights of the Order of the Thistle have assembled, and the procession leads to the Chapel of the Order of the Thistle where the new Knights are installed.
After this and during the singing of a Psalm by the Choir the Thistle Procession proceeds from the Chapel to the Sanctuary (the body of the Cathedral) where the rest of the service takes place. A Lesson is read by one of the Knights (normally the last one to be accepted into the order on the previous occasion) followed by more prayers and another hymn then The National Anthem. After the Benediction by The Dean of the Order (The Very Reverend Gilleasbuig Macmillan who is the Minister of St Giles) the Thistle Procession moves to the West Door of the Cathedral and processes to the Signet Library.
At the end of the service, the Queen, The Duke of Edinburgh and the Knights of the Order of the Thistle process to the Signet Library for a short reception.
All Members of the Thistle are invited to join the Queen for lunch at Holyrood following the Service.