Washing tent carpet, any ideas?

[MegBusset]

Our Outwell tent carpet is a bit fusty and mildewy, was going to put it in the washing machine but it won't fit! Any other ideas?!

Take it to the laundrette, or put it on the washing line, or put it in the bath and stamp on it?

I have put it in the bath to soak overnight. It has turned the water a quite revolting shade of brown