A robber described as a 'thoroughly dangerous man' who 'hi-jacked' a retired couple's car after raiding a Tesco store has been jailed for four years.

Andrew Hennells, 32, threatened a female member of staff at the customer service desk at Tesco in Gaywood, King's Lynn, forcing her to hand over £410 from the till before fleeing the store.

Norwich Crown Court heard that he then 'hi-jacked' a retired couple's Citroen forcing the woman passenger to get out of the car at knifepoint, before driving off.

The victim's husband, who had just left the car to go to the cashpoint, said his 'blood had run cold' when he saw what was happening.

Martin Ivory, prosecuting, said Hennells, of Riverview Way, Gaywood, was arrested shortly afterwards at a nearby pub.

Police said it later emerged that Hennells had boasted on Facebook about carrying out the robbery. He had posted a photograph of a large knife and a comment saying, 'Doing.Tesco.Over.'

Hennells admitted robbing the store in St Faith's Drive at about 7.40pm on February 13, and having an offensive weapon, a knife, on the same date.

The court heard he had a previous conviction for robbery in 2002 when he was a serving soldier.

Jailing him for four years and ordering that he be on an extended four years' licence, Judge Anthony Bate told him he was a 'thoroughly dangerous man.'

He said it was a brazen, and frightening incident.

He said that he had targeted the customer service desk as he knew it was just inside the main entrance of the store.

Judge Bate added that there could have been all sorts of consequences to his actions.

Jonathan Goodman, for Hennells, said it had been a 'spur of the moment' offence.

He said when Hennells 'hi-jacked' the car he was unaware there was a female passenger inside.

'He did not at that point know there was a lady passenger in there because of the way it was parked. This was a fast moving incident.'

He said another unusual aspect was that Hennells had just gone to the pub rather than make his escape.

'He went to the pub which is unusual for an armed robber who wished to escape detection.'

Speaking afterwards, Dt Sgt Pete Jessop, from King's Lynn CID, said he was pleased with the sentence. He said: 'I think it's a fair sentence for what happened. It just goes to prove that you cannot go around, seemingly on a whim, pulling a knife on members of the public on two occasions.'