William has returned to royal duties for the first time since his wife, Kate Middleton, gave birth to their third child on Monday.
He now has three young children at home - his two-day-old son, Princess Charlotte, who will turn three next month, and Prince George, four.
While at the service, William dropped a major clue about his third child's name, which is yet to be released to the public.
Speaking to guests, Wills could be heard saying the new royal baby has a 'strong name' and that Kate and the new prince were 'very well' and 'in good form, luckily'.
'Sleeping’s going reasonably well so far, so he’s behaving himself, which is good news,' he said.
Wills also met with Sir Jerry Mateparae, New Zealand High Commissioner to the UK, and the Dean of Westminster, who joked about the eagerly anticipated name, saying: 'Jerry would like it to be Jerry.'
Australian High Commissioner Alexander Downer also suggested Alexander, to which William said cryptically: 'Funny you should say that....It’s a good name,' The Sun reports.
Alexander is one of the tipped favourites, although Albert and Arthur remain the most popular among bookies.
The doting dad also revealed older siblings Prince George and Princess Charlotte are 'very happy...delighted' with the new arrival.
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