The bath is gone.

The bath has been in for over 30 years and I had forgotten that these tiles were behind it. They are about an inch thick (2.5cm) . They are on the floor in places too. The placement of them makes no sense to me or the bathroom fitter. There are areas of wooden floorboards. There are areas of floorboards that have another layer of boards underneath.  It's all very odd. I suspect I will never know.