Trooping the Colour marks the Queen's official 91st birthday, with thousands of people flocking to London to see the annual celebration and millions more watching from home.

Although the Queen's actual birthday is in April, her 'official' birthday is celebrated on a Saturday in June, and it is simply due to the British weather (not a cunning plot to get more presents). The tradition began with King George II in 1748 who was born in November and deemed it too cold to celebrate his birthday. He combined his birthday parade with the Trooping the Colour parade in June instead. It is held on a Saturday so that more members of the public can enjoy the celebrations.The annual celebration is performed by regiments of the British Army on Horse Guards Parade. It is a chance for the Queen to inspect soldiers from her personal troops, the Household Division.The tradition dates back to the 17th Century when the colours of the regiment were used as a rallying point in battle.

The Queen leaves Buckingham Palace in her carriage to take the Royal salute from the officers and men on parade at 11am, and then carries out an inspection of the troops wearing the ceremonial uniform.The Regimental Colour (flag) being trooped is then carried down the ranks following music by the bands. This year it's the 1st. Battalion Irish Guards.The Foot Guards and the Household Cavalry then march past Her Majesty, and The King's Troop, Royal Horse Artillery, rank past with their guns.The Queen then joins the rest of the Royal Family on the palace balcony for a fly-past by the Royal Air Force.

The queen also sent a message to the nation, calling for unification in these days of trial.

The Duchess was back in pink for today's Trooping the Colour

Her new dress to be a bespoke creation of Alexander McQueen's 'Pleated Skirt Skater Dress' . Pink silk-cotton-wool blend pleated skirt skater dress from Alexander McQueen featuring a round neck, a sleeveless design, a concealed rear zip fastening and a short length." The Duchess's version features sleeves and a slightly altered neckline. The paper bag waistline is a new feature for Kate — I think it's so cute!

Kate chose a cocktail hat from her go-to milliner, Jane Taylor. It seems to be another bespoke piece featuring swirls. There is another similar piece on the website that I first thought was Kate's one (the 'Seriatopora' for £552 if you're interested), but there are some differences.

She was also carrying her Etui Bags clutch again.

The Duchess wore the Queen's diamond pendant earrings again today. Kate has borrowed them twice previously. This pair does not have a known origin.

I loved The Duchess's look today!