In the short story The Horses of Diomedes, Pamela Grant is the sister of Sheila Grant and one of four "wild" daughters of General Grant, a retired Indian Army officer who lived at Ashley Lodge in Mertonshire. Poirot met her at a party thrown by Beryl Larkin.
In reality, "Pamela Grant" is likely to be a false name although the real name is not given. Like Sheila, "Pamela" was probably an ex-criminal who had been picked up by "General Grant" and employed to distribute drugs to their friends.