Mark Williams, 29, was on home leave from jail where he was serving a sentence for robbery when he kept six women and four men trapped for 15 hours in a 12ft by 8ft attic room at the surgery.
Armed police surrounded the building in Hay-on-Wye, Powys, and the siege came to an end when Williams fell asleep and the hostages pounced on him, Cardiff Crown Court was told.
He had placed his captives around the attic window so they would get in the way of any police sniper bullets.
In the hours before the siege, Williams carried out a 'cowardly' attack on his foster mother Sylvia Taylor, 60, in Llangammarch Wells, Powys. He beat her up and tried to force chocolate down her throat before leaving her for dead and stealing a car which he later sold for pounds 300, Ray Singh, for the prosecution, said.
When he tried to cash the cheque at a bank in Hay-on- Wye suspicious staff called police. But Williams produced an imitation handgun and forced Constable Kenneth Murray outside.
He let the policeman go, but moments later threatened shop manager Andrew Pattison, forcing him along the street to the dental surgery. Williams took hostage Mr Pattison, three other men and six women, aged from 20 to 64, and terrified them with claims that he belonged to the IRA and had recently killed someone with his bare hands. 'He said he was not afraid to die and would take someone with him,' Mr Singh said.
Williams admitted grievous bodily harm with intent on Mrs Taylor, kidnapping Con Murray and Mr Pattison and false imprisonment of the hostages. He received a life sentence for each offence.
Medical reports had described Williams as being unpredictable and suffering from a psychotic disorder. Mr Justice Curtis said later he would serve a maximum of 14 years. Charles Cook, for Williams, described him as 'lonely, woefully inadequate and introverted'.
After the case, Raymond White, Chief Constable of Dyfed-Powys, said he had complained to Michael Howard, the Home Secretary, over the home leave. 'Williams had an appalling record with convictions for robbery with violence committed on previous home visits from prison. He had a history of mental illness, of committing offences while on bail and of absconding from custody. To then let him out was incredible.'Reuse content