This is what remains of St Michael's church which was built in the 18th century on the site of the original 15th century building belonging to Athelney Abbey. It sits on the summit of the "mump" which, though only 24m high, stands out as an iconic landmark above the contrasting flatness of the Somerset Levels. This morning the views from the top were lovely! I posted a more distant photo of the mump here http://365project.org/julienne1/365/2014-11-09
I had never heard of Athelney until last week (I was watching something about Alfred the Great and the Somerset Marches) and now you've posted a photo. Love the framing through the arch and it's certainly set off by the blue sky.