looks like Blackthorn the fruits are sloes and used to make sloe gin. the flowers are usually before the foliage in March /april depending where you are.

the thorns are long and very sharp.

You can make sloe gin with the berries but beware suckers they come up yards away here and are a real menace.

I don't think it's a blackthorn but maybe damsons. I can magnify it on my iPad and it's more like plum leaves, plus the fruit is much larger than sloes.

You're right, the leaves do look too big for blackthorn,and also rather too bright green, but wouldn't birds eat damsons?
Tony have you tried tasting the fruit? You can always spit it out if its horrid.

but damsons don't have thorns and tony says this has thorns.

Well Tonywilson, there's one way to check - try biting one of the fruits and if your whole mouth dries up, it's a sloe, if not it's a damson. Let us know please.

Thanks for these answers. I plucked up courage and found a very ripe fruit on the ground. Surprisingly it was quite edible and plum-like but and not really tart, but there was also an underlying bitterness so I think sloe. Skins dark red and yellow flesh.

You would know if it was a sloe, it completely dries up your mouth. Damsons on the other hand, do have yellow flesh and the skins taste tarte when under ripe. Look on the bright side, you are still alive!!!