Prince Harry Was Seated at a Higher Rank Than Kate Middleton at Anzac Service: Here's Why

There is more to royal seating arrangements than meets the eye.

Kate Middleton, Prince Harry and Prince Richard, Duke of Gloucester, represented the royal family during the annual Anzac Day Service of Commemoration and Thanksgiving at Westminster Abbey on Thursday. Harry took the spot closest to the altar, with Prince Richard – the Queen’s paternal cousin who is currently 26th in line to the throne (although he’ll be bumped down a spot when Harry and Meghan Markle‘s child arrives) – beside him. Kate had the seat on the end.

They were seated in order of precedence, with the highest-ranking royal closest to the altar. Despite being married to a future king, Prince William, Kate was seated farthest away from the altar because she is not part of the royal family by blood. However, if Prince William had been in attendance, he would have sat in the top spot, with Kate next to him. (He’s currently visiting New Zealand, where he participated in remembrance services and met with victims of the Christchurch mosque terrorist attacks.)

Meghan is preparing to welcome her first child any day now, but had she attended Thursday’s service, she would have been seated next to Prince Harry and ahead of Kate.

Here’s where it gets even more complicated. Once Prince Charles becomes king, William and Kate will become the Prince and Princess of Wales. As next in line to be queen consort, Kate will only fall behind the king, queen consort (Camilla, Duchess of Cornwall) and her husband in ranking order – even if William isn’t present.

Although the royals often arrive to events in order of precedence, with Queen Elizabeth pulling up closest to the start of the proceedings, Prince Harry and Kate arrived together for Thursday’s event.

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While it was previously announced that the royal mother of three, 37, would step out to the service at Westminster Abbey – the very spot where she and Prince William tied the knot nearly eight years ago, on April 29, 2011 – it was a surprise to see Harry join her.

A royal source tells PEOPLE that Harry hoped to participate in the service, yet precautions were made in case the baby arrived.

Harry is “pleased he can attend today’s service, as planned,” the insider says. “With their baby due, his name was not printed in the program in case he was unable to do so.”

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The day of remembrance commemorates the first major battle involving Australian and New Zealand forces during World War I. It has been honored in London since the first anniversary of the Anzac landings at Gallipoli in 1916, when King George V attended a service at Westminster Abbey.

Meghan and Harry’s newly launched Instagram page, @SussexRoyal, commemorated the day of remembrance with a series of photos at related events, including last year’s dawn service and opening the enhanced Anzac Memorial in Sydney during their royal tour of Australia.