HI-TECH engineering firm Oxford Instruments has been promoted into the FTSE 250 index following a successful period of growth.

It means the firm, based at Tubney Woods, near Abingdon, is among the largest on the London Stock Exchange.

It employs 230 people at Tubney Woods, out of a total global workforce of 1,750.

In June it revealed its pre-tax profits had soared by more than 120 per cent over the previous financial year to £26.2m following a five-year plan to double the size of the company.

And its share price has more than doubled in the last year.Chief executive Jonathan Flint said: “Joining the FTSE 250 is an outstanding milestone for Oxford Instruments and something all our employees can be extremely proud of.

“It reflects the huge steps forward the group has made during recent times, successfully implementing a plan to double the size of the business and significantly improve margins.

“This achievement gives us further encouragement to stick to the philosophy that’s served us well and will ensure we remain focused on sustaining shareholder value and achieving our new three-year plan to target 14 per cent annual revenue growth and return on sales of 14 per cent by 2014.”

Since taking over, Mr Flint has transformed the fortunes of the company which was founded by Sir Martin Wood in 1959 in the shed of his garden in Northmoor Road, North Oxford. It went on to become the first commercial spin-out company from Oxford University, manufacturing superconducting magnets.

In 2006, the firm cut 60 jobs, closed its Eynsham base and declared a £900,000 loss before the five-year plan was started.