Plugged it into the three way adapter and turned it on.

Luckily I went upstairs an hour later to fetch something; dreadful smell of burning plastic; flames emerging from the adapter. It has a 13 amp fuse which had blown but the plastic casing was on fire. Pulled the adapter out; no problem; wall socket etc OK. Then I remembered - this has happened three times over the past thirty years with these three way adapters (all same brand) and I'd kept the last two. Took them all down to my friendly local hardware store today - they say it happens all the time.

Surely the fuse blowing should be enough. The plastic casing should NOT catch fire. Very dangerous.