Did you buy it from a garden centre? I have bought several from garden sales or church fete sales only to find they are squashes of some kind and not courgettes - quite exciting but not what I expected.

I agree with Cammomile, I bought a courgette plant from a local-ish market (25miles away) and so far it is 15' long. and the fruits behind any female flowers look too much like a squash. Hoping it's not spaghetti squash. But it is exciting.

Thanks for replies but these courgettes were grown from seed and I have no doubt they are courgettes. It has been suggested to me that it may be a problem associated with the use of 3 year old rotted compost which was in the trench over which I planted them. There may have been some moss in these which was treated and raked from the lawn. I have grown four plants of different varieties it appears that the Defender are the worst affected.
Any more ideas?

A picture would be interesting to see.