Simon and Michelle McWilliam are each facing up to eight years in jail after being found guilty of inflicting shocking cruelty on a defenceless child.

This vicious couple could have been prosecuted for murdering four-year-old John Smith but for a loophole in the law.

As the law stands, it is impossible to say which one of two adults is guilty if they emerge from a room and the third party, a young child, is found battered to death.

There should be an offence to cover this, such as causing death by neglect.

Former Home Secretary Jack Straw knows this only too well. It was after the last cruelty case in the Brighton area, in which three young children were found dead, that he was approached by a delegation that included The Argus.

New Home Secretary David Blunkett must lose no time in making the necessary changes to the law. There are other deeply disturbing aspects of this latest case. How did this unsuitable and unsavoury couple ever come to be accepted as suitable to adopt John?

More thorough checks are needed on any prospective adopters, no matter how plausible they may be. Had more care been taken, officials would have discovered Simon McWilliam had a tendency towards violence and cruelty.

How was it that little John was never moved to a place of safety by social workers or health visitors?

They made frequent visits and saw a catalogue of injuries. It should have been plain to anyone that something was seriously wrong in the McWilliams' house.

Yet the boy remained there, to meet his death on Christmas Eve. It beggars belief.

The main social workers were experienced with great devotion to children. Yet they believed the McWilliams, who said this young child was harming himself when he was covered with bruises and had three adult bite marks on him.

There has already been an inquiry held by Alyson Leslie. She has proposed a string of sensible recommendations.

Miss Leslie says social and health workers have to keep thinking the unthinkable in order to keep children safe. It did not happen in this case.

As in the last case, Brighton and Hove City Council has shown commendable frankness both in accepting its failings and taking action to solve them.

The council, child protection agencies and health bodies have all tightened up their practices following this case. But these practices are only as good as the people who operate them. There has been a long series of cases going right back to Maria Colwell in Whitehawk 28 years ago. The pattern has been the same in them all.

Social and other workers dealing with children have been good men and women who did not shirk their duties. But they inexplicably failed to do enough when it would have obvious to almost any parent that something was seriously wrong.

There will always be a few cases of child cruelty slipping through the net. The trouble in Sussex has been that holes in the net have been too big for far too long.

They must be closed before another child dies.