Intelligence gave Somerville warning, not certainty

What did naval intelligence contribute to Somerville's decisions before the raid?

It gave him warning and a general picture, but not certainty that the full Japanese carrier force was coming.

Somerville acted on partial information rather than facing blind surprise. Intelligence warned of a Japanese operation, although it underestimated the approaching carrier force and did not reveal the full Kido Butai. The Royal Navy had demonstrated elsewhere that it would risk capital ships and carriers when the purpose justified it, so fear of loss does not fully explain his caution. With a clearer picture, Somerville might have requested another Mediterranean carrier and assembled a stronger three-carrier group, though getting it there in time would have been difficult.