Gwain, at left, on duty in London, and below, at his new home at The Horse Trust.
It is hoped that his condition will improve by next year so he can return to the Metropolitan Police Mounted Branch to help police the London 2012 Olympics.
Jon Taylor, a sergeant with the Metropolitan Police Mounted Branch, said the period of respite should result in an improvement in Gwain's condition.
"As Gwain is a big horse and spends most of his time working on roads carrying weight, it aggravates his navicular condition. Being turned out in the fields on soft ground should make a big difference," he said.
"I'm thrilled that he's going to such a fantastic place for his convalescence."
Gwain, 14, a three-quarter Irish Draught, has been involved in high-profile police work for the Metropolitan Mounted Branch during his eight years service, such as crowd control at public demonstrations, football matches and concerts, counter terrorist patrols at iconic London sites and crime patrols in many London boroughs.
According to Jon, Gwain always remains calm even during volatile and violent situations, such as recent student tuition fees demonstrations, last year's G20 demonstrations and the Chelsea-Cardiff FA Cup match in February 2010, described by some senior police officers as the worst football violence since the seventies.
"Gwain is fearless in volatile situations and reassures the younger and less confident horses. I can rely on him if situations deteriorate as he always stands his ground and exudes confidence," Taylor said.
Gwain is often used for ceremonial duties and is regularly used in the "Grey Escorts" that precede and follow the Royal Carriages and Household Cavalry during state occasions. Gwain is also popular with the general public, who often take photos of him, according to Taylor.
"Gwain is a real show stopper. His handsome Roman nose, his size and his kind disposition have made him a great favourite with London's visitors and residents. People are always taking his photo - he's possibly one of the most photographed horses in the world."
Jeanette Allen, the trust's chief executive, said Gwain's need for a break shows that The Horse Trust's founding goal of providing respite for working horses is still as relevant today as it was in 1866, when the charity was founded.
"We ... hope the year's respite will help him recover from his ongoing health problems."
"The Horse Trust was founded 125 years ago with the aim of providing respite care for the broken-down horses of the London cab trade. The role of the horse as a working animal has changed radically since then, but Gwain's arrival shows the continuing need for respite that today's working horses have," she said.