Iraqi hotel worker Baha Mousa, 26, died in Basra in September 2003
The army general who ran UK military operations during the Iraq war has said he did not know about a 1972 ruling banning the hooding of detainees.
Gen Sir John Reith said he had been unaware prisoners were often "hooded" upon capture, but admitted he banned the practice after bad publicity.
He was giving evidence to the inquiry into the death of Iraqi hotel worker Baha Mousa in British custody in 2003.
The inquiry was adjourned until Tuesday.
Mr Mousa, a 26-year-old hotel receptionist, was found dead with 93 separate injuries after being held in the custody of the Queen's Lancashire Regiment.
The BBC's Caroline Hawley said Sir John was the most senior former military official to give evidence at the inquiry.
He was surprised when the panel told him that "in many cases" the standard practice was to put a hood on a prisoner as soon as they were captured.
In a written witness statement, he said: "If I had been aware that hooding for the purpose of interrogation, stress positions, white noise and/or the deprivation of food, water and/or sleep was being used in 2003, I would have ordered this to cease immediately."
He ordered the banning of the practice in October 2003, following publicity over Mr Mousa's death.
The then UK Chief of Joint Operations and joint commander of UK forces deployed to Iraq, said: "I decided to order the cessation of all hooding as it had become particularly emotive in light of the death of Baha Mousa.
"In any event, given the change in the nature of operations, the security reason for hooding prisoners had, for the most part, fallen away and if prisoners needed to be deprived of their sight, either for our force security or for the protection of the detained person, this could be done by way of blindfolding."
Sir John told the inquiry he had not been aware of the ruling by former Prime Minister Edward Heath in 1972 outlawing hooding.
Our correspondent said Sir John was also unaware that the Red Cross had raised concerns, several months before Baha Mousa died, about British troops hooding detainees.
Sir John said he was horrified by what happened to Mr Mousa and that he felt the reputation of the armed forces was at stake.
Only one soldier, former corporal Donald Payne, has been convicted in connection with Mr Mousa's death - he pleaded guilty at a court martial to inhumanely treating civilians.
Six other soldiers who faced a court martial were cleared on all counts in 2007.
The inquiry, which began on 13 July last year, has heard that illegal "conditioning" methods were used on the prisoners.
They included hooding, sleep deprivation and making them stand in painful stress positions with their knees bent and hands outstretched.