We’re seeing some tragic wildfires in Britain today including several involving grassland. The wooded area at Shirley Hills in Croydon does seem to be supporting the rule of thumb that our broadleaf woodlands do not themselves burn: the grass, heather and gorse that were gradually colonised by trees there in the last century are burning and in some cases burning the trees, but the fires are not spreading from tree to tree into the more densely wooded areas.