England meet South Africa in the final in Yokohama this weekend after producing a stunning display to beat reigning champions New Zealand 19-7.
Eddie Jones' side are favourites to prevail in a match against opponents who narrowly edged out Wales in their semi-final, favouring a kicking game that is in stark contrast to England's free-flowing style.
Vunipola has been a key part of that approach but, despite being on the brink of glory in Japan, he is still getting tips from the family who have travelled to support him and his brother, Mako.