My Washer smells like somethings died in it!!!

🙁 Hotpiont WM64
Having had my washer for several years with minor problems along the way, I have noticed in the last week or so that there is a terrible smell coming from inside the washer when it is empty. If I close the door it stinks when I open it but if I leave the door open it makes the conservetory smell.

The machine itself works fine and I use it most days, but the smell seems to have started since my husband did a “dark wash” (He even put his brand new England football shorts in!) I think he did it as a boil wash as it seemed to take a couple of hours – I had just come out of hospital he thought he was helping!!

Is there anything I can do to stop this smell??