Bombay duck is perhaps the smelliest substance I have ever encountered. It is dried lizardfish.
My colleague brought some into the office having found it at the back of his cupboard. It smells bad at the best of times, but when it is 5 years past its expiry date and has been microwaved, the smell is truly awful. It’s a bit like maggots and over-ripe cheese. The smell was so strong that my whole office unit fled to the outside to avoid the stench, but unfortunately the smell leaked out into the atrium of the office building and started to disturb other tenants. It was so bad that the security guard for the building obtained a can of air-freshener and walked around the building with his finger down on the button. People 50 metres away at the end of the building were holding their noses.