Sooner than it takes most dreams to turn into nightmares, the stunning replacement of a corrupt elite in Malaysia by a government legitimised by the popular will is turning against Singapore's relations with its northern neighbour.

Malaysian Prime Minister Mahathir Mohamad has reverted to form in the two months since he took over from Najib Razak. The combative times that Singapore witnessed in its dealings with Malaysia during his previous premiership are back after a happy 15-year break.