It looks like a Scots Pine to me - but I'm not a conifer expert. Does it have lots of cones?

I agree.

Having had a forest full of them at the bottom of the garden for many a year i would say that it is a Scots Pine.

As there is only one i would say that a seed was dropped by a bird

Not scots, probably Pinus strobus

It's a pine but not a Scots Pine. The leaves in the picture are long and thin, in a Scots Pine they are shorter and fatter. It looks like an American or Southern European pine tree, like a Corsican Pine, which is grown in the UK as a timber tree.

You have a nice, attractive, looking tree in your garden whatever it is.

Yes, very nice! Much nicer than the Xmas trees some people insist on 'releasing' into the garden after they've done their stuff in December!

Thank you for the replies and for sharing your knowledge and experience.
It does have a lot of cones...

The needles in the second picture are too long for a Scots. Probably one of the Mediteranean pines.

Judging by these pics this tree is a five needled pine, all hardy mediterranean pines including Corsican (Pinus nigra) are all two needled pines, so is scots! (Pinus sylvestris) highly unlikely to be anything other than a strobus. A close up pic of the cones and foliage should confirm this.