Arcs-boutants also known as a flying buttresses; these devices transmit the force of the ceiling through the wall to a counterweight outside the building. It means the walls can be thinner and allows more space inside the building. They were extensively used in mediaeval ecclesiastical buildings. However the ones you see here, at St Mary's, Beverley, were put up in the 1850s in a restoration job by Augustus Welby Pugin, his son E Welby Pugin, and Sir Gilbert Scott.
They fit in well and do look pretty cool with the light shining through.
They fit in well and do look pretty cool with the light shining through.