So, how did Rebekah Brooks end up borrowing a police horse?

Scotland Yard helped the former News International chief executive Rebekah Brooks to go out hacking, it was revealed yesterday – but the arrangement owed nothing to the interception of mobile phone messages.

Instead the Metropolitan Police loaned the flame-haired newspaper executive a loyal steed which she used to hack ("to ride a horse in the country for pleasure": Oxford English Dictionary) across the Cotswolds for nearly two years. The horse was loaned to Ms Brooks by the Met's Mounted Branch in 2008, a year after the News of the World's Clive Goodman was jailed for phone hacking. The revelation raises further concerns over the relationship between Rupert Murdoch's media empire and Britain's largest police force, which has been criticised for the inadequacy of its initial investigation into criminality at News International.

Most horses that are retired by the Met's Mounted Branch are placed with the Horse Charity Trust in Buckinghamshire. Ms Brooks is an enthusiastic horsewoman and is married to the race-horse trainer Charlie Brooks. They live on a farm near Chipping Norton, Oxfordshire, where the horse was stabled until 2010. She is also a member of the Heythrop Hunt, which is also supported by her friend and neighbour Jeremy Clarkson, the Top Gear presenter and NI columnist.

Earlier this week, the Leveson Inquiry into media standards heard that Ms Brooks, 43, had been briefed on the original hacking inquiry by a senior Met officer. She was arrested last July by police carrying out a new investigation into phone hacking and bribery at News International, having resigned from the company days earlier. Ms Brooks's spokes-man, David Wilson, claimed yesterday that the loan of the horse was nothing more than a good deed performed by the former News of the World and Sun editor. "Rebekah acted as a foster carer for the horse," he said.

When the steed was no longer fit enough to be ridden, it was sent to a retirement paddock in Norfolk where it was cared for by a serving police officer. By that point Ms Brooks was chief executive of NI and Scotland Yard was under intense pressure to reopen its investigation into phone hacking following fresh revelations.

The Met confirmed the loan of the horse in a statement. "Whilst responsibility for feeding the animal and paying vet bills passes to the person entrusted to its care at its new home, the horse remains the property of the Metropolitan Police service," it said. "In 2008 a retired MPS horse was loaned to Rebekah Brooks. The horse was subsequently rehoused with a police officer in 2010."

News of the "gift horse" caused astonishment and mirth in media and political circles yesterday. An incredulous Tom Watson MP, who has become a bitter enemy of Ms Brooks during the course of the phone-hacking scandal, tweeted: "At least the horse's head didn't end up in my bed."

For a guide to who's who at the Leveson Inquiry click HERE