An edible White Waxcap, or is it the deadly . . .

Edible or deadly ?
(Above and below.)

This was in a Barkisland garden, in fertilised, weedkilled and mown turf. It has appeared on previous years. Seems to contradict the wisdom that the waxcaps only survive in unimproved grassland.

Possibly Hygrocybe virginea Snowy Waxcap which is edible and good, according to Phillips, or is it the deadly Clitocybe dealbata or C.rivulosa described in the same book? Indistinct smell.