i swear on me nans grave

An expression usually used by chavs and the like who want to sound honest and trustworthy. Should (almost) always be interpreted as "I'm lying through my teeth".

"m8 i dont no were ur weed is i swear on me nans grave i dint steal it m8"
"kev i swear on me nans grave i aint never cheated on u"
see also: chav, charver