Blackthorn in bloom. I thought this was a dense thicket...

 Walking around the other side reveals it to be a tree sized Blackthorn fallen on its side that carried on growing. A number of smaller ones are clustered around, probably self-seeded. Prunus spinosa can be a large shrub or a small tree depending on habitat and management (or lack of).

 Hawthorn and Blackthorn were the principal components of stock-proof hedges. In the form of trees they are often remnants of old hedgerows, perhaps that is the case here? Or perhaps this one was originally planted to produce a crop of sloes? There are other fruit trees nearby.

 A collection of bee hives stands in an adjacent clearing. Today has been the sunniest day of the year so far and the bees were buzzing in and out. Blackthorn is one of the earliest of our native species to flower; the mass of blossom provides a great source of pollen and nectar.