An office manager explained away her lavish lifestyle of exotic holidays, new cars and expensive clothes as a lucky break on the Premium Bonds.

Instead, grandmother Susan MacDonald, 61, was funding her luxurious life by plundering almost £1m from her employer's accounts.

Today police revealed the full extent of MacDonald's deception after she was ordered to pay back hundreds of thousands of pounds.

The mother-of-two is serving a five-year jail term for stealing £904,426 from Abivale Veterinary Group in Abingdon while working as an £18,000-a-year office manager.

Police said her thefts went unnoticed for seven years.

She even took bundles of cash, shoved them into brown envelopes and asked staff to pay them into her bank account claiming they were personal savings.

At Oxford Crown Court on Tuesday, MacDonald was ordered to pay back £635,755 following a Proceeds of Crime Act hearing.

Dc Ian Leese described her as "cold and callous".

He said: "She was a trusted and valued member of staff and treated by the owners of the clinic like a member of the family.

"She acted in a heartless and uncaring manner. It went on for a number of years and meant the company could not pay for better equipment and staff could not get pay rises."

MacDonald was employed at Abivale's head office in Stratton Way. She was the only staff member who dealt with the accounts.

Cash takings from other veterinary clinics were sent to her office and she pocketed the money instead of placing it in the company account, police revealed.

Company accountants told the manager they could not understand why the firm was not turning over a greater profit but the takings fell below the threshold for official scrutiny, Dc Leese added.

MacDonald used the cash to buy expensive clothes and shoes, built a £60,000 extension to her house as well as a new drive, bought a fitted bedroom and bathroom and treated herself and husband Murdoch to a Toyota Celica and Land Rover Freelander.

She told her husband the money came from a Premium Bonds windfall.

But MacDonald was caught out in 2006 while on holiday in the Dominican Republic.

Another member of staff checked the accounts because she was having trouble making the totals match.

Dc Leese said: "If it hadn't been for the diligence of this member of staff she may have got away indefinitely."

MacDonald has six months to pay back £635,755 - or face a further five years in jail.

She was jailed on November 30 at Oxford Crown Court after admitting seven charges of theft.

Abivale declined to comment.