Prince Harry arrives at Invictus Games event after flying back to the UK: Duke attends talk in central London after returning to Britain without Meghan and their two children

Prince Harry has arrived in Britain alone today after flying in from California for a ceremony marking the 10th anniversary of the Invictus Games in London tomorrow.

The Duke of Sussex was pictured at Armoury House this afternoon for an Invictus Games discussion called 'Realising a Global Community', before tomorrow's service. 

The Prince is also expected to meet his estranged father the King during his trip, which follows a previous quick visit in February after Charles's cancer diagnosis.

Harry is understood to have various Invictus Games commitments today, according to ITV. Tomorrow, he is set to give a reading at a service of thanksgiving at St Paul's Cathedral marking a decade since the inaugural competition in London in 2014.

Organisers had said there was no confirmation of any other royals attending, or if Harry's wife Meghan Markle or children Archie and Lilibet would also be in the UK. 

But Harry arrived in London by himself today, and is expected to join the Duchess on a tour to Nigeria later this week with Meghan set to fly there from the US by herself.

And Harry is not anticipated to see his brother Prince William , who is scheduled to be away from the capital on Thursday and Friday, or his sister-in-law Kate Middleton whose cancer treatment continues following her revealing the diagnosis in March. 

Earlier today, Charles was photographed being driven from Windsor Castle before arriving at Clarence House in London soon after. The King later held an audience nearby at Buckingham Palace with the Prime Minister of Fiji, Sitiveni Rabuka.

The Duke has invited William and other senior members of the Royal Family to the service but none of them are expected to attend, sources told Page Six in the US.

Among the royals who could attend include his cousins Zara Tindall and Princesses Beatrice and Eugenie, but there has been no confirmation of this. Harry is expected to stay at a hotel in London because he no longer has Frogmore Cottage in Windsor.

But Charles is likely to be in London tomorrow for his usual weekly audience with Prime Minister Rishi Sunak, providing father and son with a chance to meet again.

Although Charles has been left wounded by his son's behaviour in recent years, he has always privately insisted he will keep the door open for him to at least speak.

William, however, is understood to find his brother's betrayal more difficult to forgive or even put to one side.

The Prince and Princess of Wales will be at Windsor where they have asked for privacy so that Kate can focus on her recovery from serious abdominal surgery and ongoing preventative chemotherapy for the cancer that was subsequently discovered.

It will be Harry's first visit to the UK since February when he returned for a brief trip to see his father the King following his cancer diagnosis.

It is also the first major event he has attended in Britain for some time and comes amid his ongoing a legal case about his personal security arrangements whenever he is in the UK.

It will also be Harry's first visit since the Princess of Wales revealed her cancer diagnosis.

Experts say that while he may meet his father the King, he will unlikely meet up with Kate or Prince William.

Royal author Tom Bower told MailOnline: 'I'm sure he won't see Kate. I would be surprised if Meghan came.'

Fellow royal commentator Richard Fitzwilliams added: 'Catherine is undergoing preventative chemotherapy treatment and given how deep the rift is, to me it seems unlikely.

'The only hope of reconciliation is that it would happen privately and we wouldn't know.'

And former BBC royal correspondent Michael Cole said: 'After so much bad blood, it is very difficult indeed to see any sort of reconciliation between the Sussexes and the Royal Family happening (this) week - or for the foreseeable future.'

Harry and Meghan were understood to have made contact with the Prince and Princess of Wales 'privately' after Kate announced her cancer diagnosis.

They also released a statement, saying: 'We wish health and healing for Kate and the family.'

Tomorrow's service at St Paul's, which is expected to run from 5pm until 6pm, will come two days after Harry's son Archie celebrated his fifth birthday yesterday.

Actor Damian Lewis is set to recite a poem during the service.

Representatives from across the Invictus Games participating nations, including members of the wounded, injured and sick service personnel and veteran community, will also be in attendance.

Following the ceremony, Harry and Meghan are scheduled to head to Nigeria after being invited by the west African country's chief of defence staff.

He met Harry in Germany last September at the Invictus Games Düsseldorf in Germany, which was also attended by the Duchess.

Harry is patron of the Invictus Games Foundation and last year released a documentary series with Netflix called Heart of Invictus about the athletes.

Yesterday, the Sussexes celebrated Archie's fifth birthday privately before their upcoming travel plans, reported People.

A source said a 'low-key' party was planned at the family's £12million mansion in Montecito, California.

They added: 'They'll have friends around them and Meghan's mom, Doria (Ragland). Meghan will definitely have support that weekend.'

Speaking about Lilibet, the source also said: 'They are so sweet together. Archie loves Lili. He's such a sweet boy. When she's not around, he asks, 'Where's Lili?''

In February, the Duke and Duchess both attended a launch event for the new winter version of the Invictus Games in Whistler, Canada.

Speaking to ABC's Good Morning America at the time, Harry said: The kids are doing great.' He added. 'The kids are growing up like all kids do, very, very fast.

'They've both got an incredible sense of humour and make us laugh and keep us grounded every single day, like most kids do. I'm just grateful to be a dad.'

Also yesterday, Charles and Queen Camilla celebrated the first anniversary of their Coronation, which was attended by Harry – fifth in line to the throne.

He was seated in the third row in Westminster Abbey and had no formal role in the proceedings.