Spanish slugs?

That just looks like a normal common garden slug. They are either black or red (red to orange) with an orange fringe. They can grow to 5 inches.

The Spanish slug is brown and about 3 1/2 inch to 4 1/2 inch.
Good video that shows its colour and head.
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There is a good identification guide for slugs here;
http://www.slugwatch.co.uk/?page_id=21

Punishable by squashing.

This slug (or its relatives) has been living in my compost heap for several years.  I'm kind of reluctant to kill it, but it does look very like a Spanish slug.  So does the one at the top of the thread, you can just see it's little dark horns peeping out.  I don't know who the culprits are who eat everything I leave un-protected in the garden, and who coated the tent in slime, but if this big slug is in fact eating other slugs and keeping some sort of balance, I don't want to kill it.  I kind of get the impression from what I read that if it was Spanish, I would be overrun with thousands of them by now. 

Verdict?

I agree too.

It's got the 'saddle' and the size / colour - http://www.slugwatch.co.uk/?portfolio=spanish-slug

 

Sounds like war for sure