Mystery Fruit Tree

[Myles]

Hello.
We've had this tree in our garden for 15 years and only this year has it bore fruit after a lot of blossom in late spring.
Not sure what tree it is any help appreciated! Small dark red berries smaller than the size of a 5pence piece.

 

[Owdboggy]

Bird Cherry? Prunus padus

 

[Chuck]

Looks like a Nanking Cherry

 

[alp]

Or bitter cherry, as @Owdboggy points out. Have you tried it? Is it sweet at all? Are they all this size. Birds love them. I remember after rain, all my cherries disappeared. But mine is a sweet Stella. Neighbour has a bitter one and the roots go right into my garden and I even have sideshoots springing out from a root! That's why I have decided against planting trees right into the border.