Thanks for your help everyone and in particular I appreciated the explanations of why WD40 is NOT a good idea,

However this problem has now gone away rather dramatically.

My Targus APM12US which Targus recommended for this laptop has now melted its tip into the computer housing during a recharge and the computer has stopped working completely. I Had to pull hard on the tip to get it out of the molten plastic on the Asus housing and am not sure what damage the heated tip or the tugging has done to the DC jack!

Sorry this question has gone OT a bit.