I wonder if William will lay a wreath at The Cenotaph on behalf of his father at the Remembrance Sunday Service?
I don't recall substitutes laying wreaths for other members of the Royal family in the past when they have missed the Cenotaph service because they have been attending services elsewhere. The only exception would be the Queen who doesn't lay her wreath on her own behalf but lays it on behalf of the nation.
In any case, the Prince of Wales will lay his own wreath, just not in London. I think William will lay his wreath on his own behalf only.