My guess is that a long time ago there was a fire in part of our house and what was the top storey was capped and the floor replaced with thick slabs of concrete. This was then sealed over with bitumen and left as a flat roof, with traditional pitched roofs on either side.
Now, however, it seems something is failing and the roof has started to leak. It's always pooled water on the top to half an inch or so, but the last lot of heavy rain caused a stain on the ceiling underneath. That was easily redecorated, and I've made sure the drain to the gutter is properly free flowing now, but I don't want it to start again.
What's a good way to seal this roof so that doesn't happen again? I've used flash-band to patch up a couple of obvious cracks in the bitumen but I'd rather have something more permanent.