Northern Ireland’s police chief has said he believes the IRA was behind one of the UK’s biggest ever bank robberies. The announcement is likely to set back efforts by the IRA’s political ally, Sinn Fein, to re-enter the province’s power-sharing government.Chief Constable Hugh Orde said: “what I can say is that on the basis of the investigative work we have done to date, evidence we have collected and exhibits we have collected and bringing that all together and working through it, in my opinion the Provisional IRA were responsible for this crime and all main lines of inquiry currently undertaken are in that direction.” The IRA has denied involvement in what was a complex and meticulously planned robbery of the Northern Bank’s main branch in Belfast last month. It is thought the thieves escaped with the equivalent of around 38 million euros. The gang had forced two senior bank staff to open the vaults after taking their families hostage. The Northern Bank has said it will withdraw its newly-made sterling notes from circulation. Orde said that action would make the robbery the largest ever “theft of waste paper”.