A hedge of prickly Blackthorn (Prunus spinosa) runs along one side of the allotments. Blackthorn was a traditional choice -along with Hawthorne- for stock proof hedges and is still widely used as a hedging plant.

 Actually at first glance I took this to be a Hawthorn but I think I'm right in saying that P. spinosa has yellow tipped stamen (as seen above) rather than pink and flowers before it comes into leaf rather than after which differentiates it from Crataegus monogyna.

Honey bees were being busy bees on the flowers.

Note the bulging pollen sac on the hind leg.

NB Blackthorn is also known as Sloe so assuming my ID is correct these flowers should produce a crop of Sloes in the autumn in which case a bottle of Sloe Gin might be in order.