A mother's mercy plea for a man who admitted causing her son's death in a river accident failed to stop him being jailed for four years today.

Engineer Sean Robinson, 35, was sentenced following the death of his lifelong friend Mark Smith.

Mr Smith was catapulted into the River Tyne as the inflatable Robinson was driving ''recklessly'' hit a boat carrying Sea Cadets as young as 11.

At Newcastle Crown Court, just 150 yards from where the collision happened last August, there were cries from the public gallery as Mr Justice Bennett passed sentence for manslaughter.

Robinson, the father of a two-year-old daughter, will appeal against the ''shocking'' sentence, his solicitor said later.

Eric Elliott, defending, had told the court Mr Smith's mother Sheila had come to rely upon the defendant for support after the accident.

In a statement, which divorced Mrs Smith was not required to read out in court, she said they had comforted each other.

Mr Elliott said today: ''She has had an appalling time and she has been helped and eased through the trauma by the defendant.

''Without the rock of the defendant's closeness and companionship she will continue to suffer even more greatly than she has suffered to date.''

The court heard that Robinson, of St Peter's Basin, Newcastle drove his inflatable a few miles along the River Tyne to a pub on the city's popular quayside.

With him were his friends Mr Smith, 29, from Dunston Hill, Gateshead, and Malcolm Harper. At the pub he drank a pint of lager and at least one bottle of red wine, the court was told.

When Mr Harper was ''boisterous'' with a group of women the trio were asked to leave, although Robinson and Mr Smith were said to have tried to calm the situation.

The trio got into Robinson's boat and sped away at approximately 28mph when the local speed limit was six knots or 7mph. He was also driving on the wrong side of the river.

Robinson admitted to police afterwards he would not have driven a car after drinking that amount but said he was still capable of controlling the boat.

He did not see a small boat carrying three Sea Cadets and two adults, which was acting as a safety vessel for other cadets carrying out manoeuvres on the river.

The court heard how teenager Fiona Robinson was at the controls of the boat and when the inflatable was seen to be on a collision course she put the boat into reverse, making it stop and possibly averting a worse accident.

Robin Patton, prosecuting, said: ''Had she not reversed that boat, we may have had a greater tragedy than we already have had to deal with.''

The accident, just upstream from the new Gateshead Millennium Bridge, caused Mr Smith to be thrown into the river and despite the efforts of Robinson and those on the sea cadet boat, his body was not found until a week later.

Mr Harper, who was thrown on to the other boat, and the defendant also sustained injuries in the collision but the occupants of the other boat were not badly hurt. Judge Bennett said he gave the defendant credit for pleading guilty and for his obvious remorse.

He paid tribute to Mrs Smith for the ''impressive'' statement she made in pleading for Robinson not to be jailed. The judge said Robinson had driven recklessly, had consumed alcohol which dulled his reactions, and was going at an excessive speed.

He told him: ''I will extend to you a measure of compassion because you have been a great support to Mrs Smith and because of your very great remorse.'' After the case Detective Chief Inspector John Lingwood said: ''This is a tragedy for everyone concerned.

''It goes to highlight to us all not only the dangers of drinking and driving any type of vehicle or vessel but also the dangers presented by the River Tyne.

''Nothing that the judge could sentence Sean Robinson to can bring Mark back and Sean will have to live with the consequences of killing his best friend.''

Defence solicitor Clive McKeag said his client, who had expressed his remorse repeatedly, will appeal.

''Mark Smith's mother appealed to the judge for leniency,'' he said. ''The sentence imposed has shocked all those involved in the defence and indeed, Mark Smith's mother is also shocked and an appeal will be lodged forthwith.''