My Open Fire Back Boiler appears not to be working?

I recently decided to use my open fire back burner for the first time. The house is 22 years old and I've lived there for 8 years. A electrical switch on the wall adjcent to the fire wasn't working and apon inspection I discovered that the fuse was missing, to which I replaced it. However, even though the switch appears to be working and I had the open fire lit for 4-5 hours, none of my radiators became warm, let alone hot. What could be the problem?

David
February 2012