Nelson Mandela
A nickname given to MDMA.

In the UK MDMA is often referred to as 'Mandy'. After a while instead of 'Mandy' the term 'Mandela' was used. Hence the term Nelson Mandela was born.
'Alright mate, wanna buy any Charly?'
'Nah not tonight bruv I'd rather get on the Nelson'
'Nelson?'
'Yeah you know Nelson Mandela! Mandy! MDMA!'