Although Trooping the Colour is also known as the Queen's Birthday Parade, this prime piece of pageantry doesn't take place on Her Maj’s actual birthday (that's on April 21) but on her official birthday, a Saturday in June being more likely to provide decent weather for the proceedings.
Carried out on Horse Guards by fully operational troops from the Household Division (Foot Guards and Household Cavalry), Trooping the Colour is a military tradition that dates back to the early eighteenth century. Originally it was all about helping soldiers to recognise their own standard in the chaos of battle. Now it's an opportunity for some seriously impressive marching manoeuvres and an excellent opportunity for royalty spotting (other members of the royal family attend, as well as the sovereign). For many years the Queen strutted her stuff on horseback but these days she travels by carriage. After the parade, the royals head back to Buckingham Palace for balcony photo op and there’s usually a fly-past at 1pm to wind things up.
You can watch along the Mall or from the edge of St James’s Park for free. But you need to arrive well before events begin at 10am to be far enough forward to get a good view so it will come as no surprise that the limited grandstand seating is highly sought after. Applications for tickets are invited in January and February each year and the ballot takes place in early March, after which successful applicants are notified and payment is requested.
To apply, write to The Brigade Major, Headquarters Household Division, Horse Guards, Whitehall, London SW1A 2AX, stating how many tickets are required (max 3 per application), enclosing an SAE.
You can also watch the rehearsals, known as the Major General’s Review (Saturday May 30), and the Colonel's Review (Saturday June 6). The scale and splendour of the event is the same but the Queen isn't involved.