Tree with white knobbly bark and triangular toothed leaves.
No interactions present.
Unfortunately there are a significant number of introduced birch species being planted in Britain, some escaping into the wild. This doesn't look quite like B. pendula to me. The leaf outline is slightly convex, and the photograph of the tree suggests it doesn't have pendulous branches.
At present there is not much that can be done with them - though I believe that a forthcoming account will cover some 30 or so species!
Lat/Lng: 53.3873, -2.9248
OS grid ref: SJ385882
Park in suburban district of Liverpool. Former grounds of Rathbone family home, sold to council in 1897. Mix of wooded areas, walled garden, lawns and lake.