I've always thought I was being a sensible grown up by diligently emptying the door filter of my tumble dryer on a regular basis and removing all the fluff so it was good and safe and all that...go me!
Today, with some lockdown time on my hands I was giving it a spring clean and pondered what the flap at the bottom of the dryer was hiding.
I opened it up to discover another large filter which could be slid out. It was covered in a layer of damp, dusty grot with added slime around the seal for good measure 
It's now had a good clean out. I've discovered £1.01, a zip attachment and a false finger nail (thanks Dd).
I've also spotted a neat little diagram that tells me I should have been cleaning this out once a month.
I now feel a bit
that it's taken me about 3 years to find this grot spot. (But I did enjoy the manky mess). Am I the only person who didn't know about these secret places in tumble dryers. I am agog!