looks like it might be a black poplar. produces white fluffy seeds in the late spring.

Still baffled. Are the things that look like tiny acorns fruits, nuts or buds?

Hi, looks as though it might be a hazelnut tree, Derek.

Defo not Hazel. leaves are wrong shape and wrong arrangement on the stem.
And the leaves are the wrong shape for Black Poplar.
The leaves remind me of one of the Prunus , but the darkness of the bark is a concern.
Still not found a match yet.

I put black poplar when the question appeared the first time, and then changed my mind and deleted it. Bit of a puzzle innit?

I am beginning to think that it may be a Willow, Salix, possibly a hybrid. The leaves look like S. cinerea, but the darkness of the bark is more like S. caprea.

A better picture might have helped. My first thought was some variety of oak as the fruits looked like acorns at a distance. Still not quite sure but could it be Rhamnus Frangula, Alder Buckthorn which is a native.

Surely the leaves are the wrong shape for Rhamnus, they are much wider across the middle than these?
Very difficult, is it not?

Owdboggy, this had got me foxed so I emailed a colleague who is an experienced plantsman and he has gone for Salix caprea (Goat Willow) so I would guess you're right.

That would explain the little buds at the base of the leaves anyway.

Cheers folks. It was the height of the tree which made it more difficult as S. caprea is normally a fairly small shrub, at least it is in my experience.
We is gettering gooder at this id thing.

Snap OB!