What happens if a substandard power lead is actually used.
A moderate current is passed through the power lead and the results are not what anyone would want.
With 13 amps applied, the temperature of the flex exceeds 70C after just 3 minutes. Bearing in mind the plug has a 13A fuse in it, this is not overloading anything.
At 20 amps the cable temperature quickly exceeds 100C, and at 25A the cable smokes and bursts into flames.
25 amps may seem excessive - but the 13A fuse supplied with it was fake and of indeterminate rating, and most socket outlets in the UK are connected to 32A circuits.