The Duke of Cambridge said his spaniel Lupo was "coping alright" with the new addition to the family.
Prince William said, "As a lot of people know who have got dogs and are bringing a newborn back, they take a bit of time to adapt, but he's been alright so far."
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He said people have handed over thousands of pounds in good faith, only to find the advert has nothing to do with Mr Lewis or his company.
The memorial service will be attended by Prince Harry and Meghan Markle.
David Browning admits manslaughter by diminished responsibility but denies murder.