"The title is not automatic and is not heritable; it merges into the Crown when a prince accedes to the throne, or lapses on his death leaving the sovereign free to re-grant it to the new heir apparent (such as the late prince's son or brother). Prince Charles was created Prince of Wales on 26 July 1958, some six years after he became heir apparent..."
Note that Prince Charles (born 1948 and heir apparent from 1952) was CREATED Prince of Wales in 1958, having previously (in 1952) been created Duke of Cornwall and Duke of Rothesay. So between 1952 and 1958 there was no Prince of Wales although there was an heir apparent. And the Queen might have withheld the title for ever.
Also, "the title of the heir to the throne" can just as well be Duke of Rothesay, the Scottish title for the heir apparent.
The question can easily be amended to "what title does the monarch usually grant the heir apparent". Both Prince of Wales and Duke of Rothesay should be accepted as answers.
The other thing is that horse-riding should be accepted for 'equestrian'
Or, for that matter, Westminster Bridge. haha
The Queen was heiress presumptive and she was never Prince or Princess of Wales. She was HRH Princess Elizabeth of York, then HRH The Princess Elizabeth, then HRH The Princess Elizabeth, Duchess of Edinburgh
George VI was Duke of York when he was the heir
Queen Victoria was HRH Princess Victoria of Kent when she was heiress
Prince Charles was simply HRH Prince Charles of Edinburgh, followed by HRH The Prince Charles before being made PoW in 1958. If he'd ascended the throne before that, he would have never been PoW
George VI was Duke of Clarence