At the time that I started the... the tumour immunology unit in University College, the dominant idea was immune surveillance. The idea was I think actually proposed by Burnett, that what we see in the way of cancer development is the tip of the iceberg and underneath there is a huge number of malignant transformations which occur in the body which are then obliterated, defended against by the immune system which eliminates them. That idea may still have a grain of truth in it, and it certainly does for viral cancer where the defence is against the viral antigens, but in a general way it sunk without trace when the genetic immune suppression came to be used. Immune suppression could be produced in a mouse by all sorts of mutants and in man it occurs spontaneously but rarely, and the genetic... genetically immunosuppressed individuals, be they mice or be they man, did not develop the sea, the raft of cancers which the immune surveillance theory predicted. And that was more or less the end of that theory, and I think the timing of that I remember quite accurately because it was work... the work in man was... immunocompromised individuals in man, became quite clear by 1980, and that left tumour immunology wondering what their agenda was and should have been. I did one smart thing.