Possibly prunus cerasifera ("pisardi" if it's a purple leaf one) Not a good photo though

Could it be a blackthorn (sloe)? Any chance of a close-up of the blossom?

If it is a free standing large tree then Andy's suggestion of prunus cerasifera is a good one, correct full name depends on leaf colour, as he suggests. The blackthorn tend to be smaller shrubby trees - lots about along motorways and hedges at the moment. Can you see if it has thorns along the branches? This will give us a clue ... no thorns ... prunus variety, but with thorns ... blackthorn.

Blackthorn's not out yet in Cornwall.

Thank you all. I shall post a picture of the blossom. Oh, there are no thorns.

That's definitely not blackthorn.

Just noticed the prunus cerasifera pisardi (purple leaves) in flower down our road (Lewes, Nr Brighton) so i'd put money on that being the one.

Hi Andy,

I'll have a look at the leaves and let you know. How much did you bet, by the way?!!

Hello ... I'd bed prunus, as the flower picture is clear. Thought of damson but the flower centre not the same.

Thank you all. So, shall I tell my friend who asked me what it was after seeing my pictures on Facebook that it is Prunus?

Been out today, and couldn't believe my eyes - there is a beautiful one of these, covered in blossom just yards from our house. Never noticed it before. I must go out tomorrow if the weather permits and have a closer look.

Go for prunus!