Pretty white flowers growing in the cemetery hedge

I'd never noticed this shrub growing through the hedge, with its roots in the cemetery. I saw it from the footpath leading between Daisybank on Horns Road and the kissing gate taking walkers down into The Heavens, which may seem like a non-sequitur, but it isn't.

The cemetery is owned and managed as a nature reserve so it has an interesting selection of wildlife including glow worms, adders, lizards and limestone loving plants. However I've no idea what this shrub is.