This is another ex-church that is being redeveloped. They're making it into lots of houses. There are plans for "Conversion of the church of St Mary the Less into five residences; restoration and alterations to existing church".
It used to be called St Mary the Less - I think it's even more "Less" now! I had to hold on really tight to the barrier so I didn't fall off. There are lots of notices here, but not really church-y ones.