She joined Queen Consort Camilla to support the walking members of the Royal Family during proceedings.
Meghan, Duchess of Sussex joined Sophie, Countess of Wessex in a separate car behind the two other royals.
They travelled in a cortege with police escort vehicles past the Grand Entrance at around 2.45pm.
It came as silence fell among the thousands-strong crowd as a muffled drum draped in black was beaten at 75 paces per minute before Queen Elizabeth II's coffin appeared.
Princes William and Harry joined King Charles III, Princess Anne, Prince Andrew and Prince Edward on foot alongside Peter Phillips, Vice Admiral Sir Timothy Laurence, the Duke of Gloucester and the Earl of Snowdon.
Kate, Princess of Wales with the Queen Consort
SARAH MEYSSONNIER
Meghan, Duchess of Sussex alongside Sophie, Countess of Wessex
SARAH MEYSSONNIER
Queen Elizabeth II's coffin was draped in the Royal Standard, with the Imperial State Crown on a velvet cushion with a wreath of flowers atop, and carried on a gun carriage of King’s Troop Royal Horse Artillery.
The crown was positioned in front of a wreath made up of white roses, spray white roses, white dahlias and a selection of foliage, including pine.
The Band of the Scots Guards and the Band of the Grenadier Guards played funeral marches throughout the procession, starting with Beethoven’s Funeral March No.1.
People could be seen standing on buildings and balconies overlooking The Mall as onlookers flocked to the capital to pay their respects.
It comes after William, Kate, Harry and Meghan stunned royal watchers with a rare display of unity on Saturday.
The quartet – once dubbed the Fab Four – arrived in the same vehicle and greeted well-wishers for around 40 minutes before William hopped into the driver’s seat of the Audi with his wife in the passenger seat, and his brother and sister-in-law in the back.