We have all known types for Cnut listed in the England catalogue and there is no match with your coin. I'm no expert but the combination of the crude portrait and the voided long cross doesn't look like any English penny I have seen before, but I could be wrong.
Just because you can't see it ... doesn't mean it isn't there - Anon.
It looks like a Hiberno-Norse 'Long Cross and Hands Coinage', c.1035-1060. I'll look into it a bit more later today. It is a crude Irish imitation of Anglo-Saxon coinage.
Looks like you have Sp#6132. Worth £200 in fine condition and £475 in very fine condition. Its one of Irelands earliest coins, they only started striking them in c.995.