It's being widely reported that Boris was booed on arrival at St Paul's today.
This article sheds a tiny bit more light on Mordaunt:
Boris Johnson is sleepwalking into an ‘inevitable’ vote of no confidence
www.thetimes.co.uk/article/531025de-e349-11ec-baab-53d14c642149?shareToken=b261ba1ed9fbd5257a4e78a68f73682c
"Within government Penny Mordaunt, a trade minister, has the support of a number of Tory rebels, particularly among Scottish conservatives. Friends have insisted she is loyal to the prime minister. Liz Truss, the foreign secretary and Nadhim Zahawi, the education secretary, are seen as potential rivals."
A potential candidate who insisted TWAW from the despatch box with support in Scotland, a nation likely pressing ahead with self-ID in spite of majority opinion against doesn't inspire confidence.