04/26/2013 AT 01:50 PM EDT
When Harry met nappy!
will soon be an uncle
– and he's already learning how to change diapers, or nappies as they're called in Britain.
With his sister-in-law, the Duchess of Cambridge
, expecting her first child in July, Harry, 28, got a chance to try out his skills Thursday while visiting Headway, a charity that helps brain-injury survivors.
Patients there recuperate by doing simple physical tasks like a diaper change. Harry practiced on a baby doll, and even managed it one-handed – though he fumbled quite a bit along the way.
"This is exactly how my brother is going to be," the prince joked as he struggled to fasten the diaper.
"All the mothers will be saying, 'Don't let him near the children!' "