This is the ruin of Kenilworth Castle in Warwickshire.
When it was occupied the field was flooded as a man-made lake as part of the castle defences. The castle in its prime must have looked magnificnent reflected in the water. Easy to understand why it was a favourite with previous owners - Robert Dudley in the 1500s and 200 years earlier, John of Gaunt.
In their own times they were both among the richest men in the land and they lavished money on the castle to re-model it and make it a luxurious palace.
It's good to be rich :-)