Unidentified tree, possibly ill?

[Nickt9]

Hello and thanks for looking. 
 

This Hertfordshire tree atop a big hill next to ancient woodland seems very late to the party in terms of leafs. I don’t know what kind it is. It is in my back garden. The previous owners of my house cut back all the branches below a certain height to preserve a view. I’ve tried to get a telescope to see the branches up top and it looks like they’ve got buds, but why so late? 
 

At head height there is some minimal new growth (pictured). There is also a weird white sheen on the bark low down the tree, not sure if that is a sign of ill health. 
 

Anything pointers/insights as to what I can do to help/save it (if that’s even needed) would be much appreciated. 

Thank you so much! 

[openspaceman]

It looks like a tree of heaven, ailanthus altissima to me, the white on the bark may be a scale insect but give it a week or two and look at the crown again.

[Mick Dempsey]

Could be simpler, a sycamore?

[Boo Who?]

It looks like a sycamore to me - go for a wonder around the woodland and see if and how many others are still only just starting to flush, I am sure there will be a few.
I’ve been working in a woods the last few weeks and have been watching - there is a wide gap between all the trees of each species within the woods from the first tree to burst to ones that are still waiting.
I was wondering if perhaps these are single sex trees that are holding on, but haven’t got around looking into it at all yet

[The avantgardener]

Definitely Sycamore, they are in full leaf here in Sussex, maybe just a bit behind.

[Nickt9]

Thanks so much for all your replies. It is 100% not a sycamore. We had one Autumn with it and if it was a sycamore I’d have recognised and remembered the distinctive spinner seeds/leaves etc. It’s something else but plumbing the depths of my memory I can’t recall the seeds it gives off. When that small bud unfurls I’ll post a pic and then it will probably be obvious. 
 

All other trees in the area are fully green. 

[se7enthdevil]

looks a bit like a beech to me with bark that smooth.

[The avantgardener]

The bud formation is definitely an Acer, still think it is Sycamore.

Edited May 8, 2020 by The avantgardener

[Gardener Joe]

I agree with The Avantgardener... I'd say sycamore ?

[gary112]

Sycamore