It has been a long and sometimes frustrating road for Mr John Knowles and Pudsey MP Paul Truswell, but all being well, by Tuesday their crusade to close a loophole in the licensing laws should have achieved its very worthwhile goal.

That is the day the House of Lords is expected to give its assent to a Bill which will make it possible to prosecute off-licence staff who sell alcohol to under-18s.

When the campaign began three years ago following the death of Mr Knowles's 14-year-old son David, who was crossing a road after twice being sold alcohol at an off-licence, many people believed that staff already were banned from selling to under-age drinkers.

However, David's death exposed a major flaw in the legislation. Only staff employed by the licensee are covered. The law does not apply to staff employed directly by the head office of a national company.

It is fortunate for other parents and youngsters that Mr Knowles was able to channel his grief into positive action. If the vote goes as hoped, there will be no way that shops and stores will be able to shirk their responsibilities. In future they will all, without exception, have to ensure that the person standing at the other side of the counter seeking to buy alcohol is 18 or over.

Young people do sometimes behave recklessly and irresponsibly. That is part of the nature of youth. It is the duty of adults to try to protect them from themselves. This important change in the law will reinforce that duty.