Three men were jailed today for their parts in what a judge described as a ''cruel and callous'' gangland killing.

The convictions ended a huge security operation which brought daily disruption to roads across the north of England.

Dale Miller, Edward Stewart and Michael Dixon were sentenced for their roles in the death of Freddie Knights in September, 2000.

Mr Knights, 38, was shot in the head outside his mother's home in Newcastle upon Tyne as he called to collect birthday presents for his 11-year-old.

The three-month long trial at Leeds Crown Court has seen a massive armed security operation with a helicopter-escorted convoy of prison vans and police vehicles bringing Leeds city centre to a standstill twice a day and also affecting traffic on motorways across Yorkshire.

Inside the court building dozens of police armed with automatic weapons and carrying gas masks have watched as special searches produced large queues for lawyers and other court users.

Officers even video recorded the daily queues to gain entry to the court room.

Today Miller, 38, of Cromwell Avenue, Gateshead, was jailed for 16 years after the jury acquitted him of murder but found him guilty of manslaughter.

Stewart, 39, of Wickham, Newcastle, was also cleared of murder but found guilty of manslaughter and jailed for 13 years.

Dixon, 34, of Blackwell Avenue, Walker, Newcastle, was acquitted of murder and manslaughter but found guilty of conspiracy to cause grievous bodily harm with intent. He was jailed for nine years.

Another man, John Henry Sayers 38, of Coquet Terrace, Heaton, Tyne and Wear, was acquitted of murder and all other charges amid chaotic celebrations from his family in the public gallery.

A fifth defendant, Lee Watson, 30, of Cedarwood Road, Gateshead, admitted murder and gave evidence for the prosecution in the trial. He is due to be sentenced at later date.

The prosecution alleged Miller was paid to kill Mr Knights following gangland rivalries about drug dealing and protection rackets.

Today the judge, Mr Justice Brown, told him: ''It's clear to me on all the evidence that this shooting was a gangland criminal activity.

''I have little doubt that you were paid by someone to ambush and shoot a defenceless man with a sawn-off shotgun.''

He added: ''It was a callous and cruel attack planned to be carried out on the doorstep of victim's mother.

''The gun was loaded with large calibre shot. Whether you knew that or not was immaterial.

''At close range your victim had no chance. You shot at him twice and with the second one shot him in the head.

''It may well be you had no intention to shoot him in the head but merely to shoot him and cause him some injuries.

''There's no basis by the jury's verdict to say this was just a shooting to frighten.''

The jury rejected the prosecution's case that Sayers masterminded the killing. Sayers insisted he had an alibi and accused Northumbria Police of setting him up.

The court heard Stewart was the getaway driver and Dixon provided support and back-up.

West Yorkshire Police and the Prison Service today refused to comment on the cost of the security operation, which saw defendants brought daily from prisons including Wakefield, Doncaster and Full Sutton, Humberside, nor the reasons for it.