Meghan Markle and Prince Harry have arrived at their last official engagement as senior members of the British royal family.

The couple joined the Queen at the Commonwealth Day service at Westminster Abbey, which takes place on the second Monday in March.

The Duchess of Sussex, 38, looked radiant in a green dress from Kiwi designer Emilia Wickstead with a matching William Chambers fascinator.

In contrast to last year, Harry and Meghan, along with the Duchess of Cambridge and Prince William, did not join Her Majesty's procession through Westminster Abbey.

Instead, they were shown to their seats - with tradition dictating that sixth-in-line Harry sit with Meghan in the second row of seats behind the Queen, Prince Charles, the Duchess of Cornwall, William and Kate during the service - rather than waiting for Her Majesty's arrival and walking in behind her.

And in a last minute change, William and Kate also did not join the 93-year-old monarch in the procession.

A source said the sudden amendments were made on Sunday - the day before the event, despite the Order of Service already having been signed off and printed.

Kensington Palace and Buckingham Palace have not commented as to why the switch was made.

Charles and Camilla, clergy, Prime Minister Boris Johnson and the Commonwealth Secretary General took part in today's procession.

The royals and other guests then listened to international boxing champion and Olympic gold medallist Anthony Joshua deliver a reflection, before singers Alexandra Burke and Craig David performed to the 2000-strong congregation.

About 45 minutes before the royals arrived, Cameroon protesters tried to storm the security fences outside Westminster.

Police later confirmed two people had been arrested at the scene.

Today's service marks the last joint appearance the Duke and Duchess of Sussex will be making before stepping back as senior royals and starting fresh in Canada, where they aim to become "financially independent".

It is also the first time Meghan and Harry have reunited with William and Kate since the Megxit fiasco, and amid long-running reports of a family feud.

The Sussexes are closing their Buckingham Palace office on April 1 and heading back to Canada, where they wish to raise their child, Archie, away from the spotlight.

The couple has had a tight schedule in the past few days during their "farewell tour", starting at the Endeavour Fund Awards on Friday, where the duchess wore a striking blue Victoria Beckham dress.

Meghan then made a private visit to the National Theatre, of which she is a patron.

On Saturday, Harry attended the official opening of the Silverstone UK Experience Museum, while Meghan surprised kids at a school in East London for International Women's Day, where a schoolboy managed to steal a kiss before telling his peers, "She really is beautiful, innit?"

That evening, the Sussexes received a resounding standing ovation at the Royal Albert Hall as they entered the royal box for the Mountbatten Festival of Music, where Meghan stunned in a red Safiyaa cape dress.

While it wasn't in their official public schedule, Meghan and Harry attended church at the Royal Chapel of All Saints in Windsor on Sunday, alongside the Queen.

It was the first time Meghan had seen the Queen since they announced news on January 6 of their decision to step back the royal family.

The Commonwealth Day service is attended by heads of government and representatives of the 54 countries of the Commonwealth.

In recent years the service has been broadcast live by the BBC and has attracted contributions from Ellie Goulding, Sir Richard Branson, and Nobel Peace Prize laureates, Malala Yousafzai and Kailash Satyarthi.

The royal couple attended last year's service when Meghan was pregnant with Archie.