BBC reports that among the guests are US television star Oprah Winfrey and actor Idris Elba. 

The couple will wed at noon before travelling through the town. St George's Chapel has been filled with white garden roses, peonies and foxgloves, branches of beech, birch and hornbeam, crafted by floral designer Philippa Craddock. 

Prince Charles will walk Markle down the aisle, after her father, Thomas, was unable to attend for health reasons. 

In her vows, Markle will not promise to "obey" her husband and Prince Harry has chosen to have a wedding ring. Markle's ring has been fashioned from a piece of Welsh Gold, gifted by Her Majesty The Queen. 

Prince Harry's ring will be a Platinum Band with a textured finish. 

Thousands of well-wishers are still arriving in Windsor, while hundreds more camped out overnight to secure the best viewing spot.

As many as 100,000 people are expected to line the town's streets.

BBC