They're both lovers of Jimmy Choo. The Duchess of Cambridge owns the brand's Vamp skyscrapers and Rebecca Adlington was presented with a pair of the label's golden heels by her local mayor to mark her victories at the 2008 Beijing Olympics.
So the royal will take a keen interest as the swimmer defends her 800m freestyle title in London – one of 30 events at the Games that she and Princes Willam and Harry will attend between them.
Kate, the former captain of her school hockey team, will also watch the women's hockey and sailing teams.
And together with William she will be in the royal box at Wimbledon for the tennis.
Meanwhile, her brother-in-law Harry may renew friendships he made in Rio de Janeiro when he met members of the Brazil volleyball team. Brazil are thought to be contenders for gold and the Prince will be in the stands on August 8 for the final.
He is also likely to see Usain Bolt run in the 100m final days earlier on August 5. The Jamaican sprinter tutored Harry in his special 'lightning bolt' celebration move on his Jubilee tour of the Caribbean.
A St James's Palace spokesman said the royals had picked out events in which they had a personal interest and also "to support Team GB as much as possible".
One competitor who may get rather louder cheers than others is horsewoman Zara Phillips. The trio will make four visits to the equestrian centre in Greenwich to support the Princes' cousin, who is taking part in the Olympics for the first time.
On Monday and Tuesday they will be joined there by the Prince of Wales and the Duchess of Cornwall.
The royals are also planning to drop in on the Olympic Village, an impressive 36-hectare complex which will house 17,000 athletes and officials from 203 nations.
On the final night Kate and Harry will also take pride of place at the closing ceremony. William is unable to make the spectacular extravaganza on August 12 because of his duties as a search and rescue pilot in Anglesey.