Being a Scouser and not being fully clued-up in relation to the north east of England, I looked for a definition of "Mackem" and subsequently found two in the Urban Dictionary which Rob might like:
Mackem "A born and bred resident of the largest city in the north east of England (unlike the common misconseption that Newcastle is) and largest ship building town in the world. Rider of the bittersweet emotional rollercoaster that is the life of a die hard supporter of Sunderland Asociation Football Club as all true Mackems really are and don't just decide to switch teams because ones doing better than the other. NOT TO BE CONFUSED WITH A GEORDIE!"
Mackem: " A demi-god worshipped by ancient civilisations as the epitome of wit and sexual prowess. Romans and Vikings colonised the area in the hope of developing a race of supermen to help them in their ambitions. The word is based on a blend of Roman and Norse, and means "astonishingly well-endowed, funny and attractive angel on a temporary visit from Valhalla."