Any ideas on why this happened?

[RhapsodyandAshe]

Tried to turn on my space heater this morning, which was plugged into a multi socket, it wasn't turning on so tried unplugging it and it would not budge. All the other plugs came out no problem but I had to lever the space heater plug out (with multi socket unplugged).
I've plugged it somewhere else and it is working and comes out with no difficulty. I've taped over the socket it was in where I could not get it out but WTF?!?

I wondered if maybe it’s slightly melted the inside of the socket. My ex once told me that heaters are best plugged straight into a mains socket rather than a multi socket but I can’t remember why!

We had a fan heater that started melting a socket in a 4-way adaptor once, just the plastic it sits in.

Plugged it in elsewhere and found the plug was getting warm when using it, therefore the metal pins would have been warm too. When unplugged felt the pins and sure enough they were heating up, therefore would be heating the socket. Could be what's happening with you.

I think that is the problem, examined it in a better light and it has indeed melted slightly, bugger.
Guessing I should be replacing the cord if I want to continue using.