Two plaques at Robert Manning College – one marking half a century at the Edinburgh Crescent site and a replica of an original which celebrated the school's move 50 years ago – were unveiled by Lady Willoughby de Eresby.

The original plaque was unveiled in 1958 by the Earl of Ancaster, Lady Willoughby's father, when Leslie Day was headteacher of what was then Bourne County Secondary School.

It went missing during alterations to the building about five years ago when it was taken away to be cleaned.

One of the longest serving members of staff is examinations officer Derek Bontoft, who has been involved with the school for almost 50 years.

He was appointed by Mr Day 44 years ago as a geography teacher.

He said: "I changed subjects and became a maths teacher. After that I was head of maths and 20 years ago I took on the role of deputy headteacher."

Although no longer a deputy headteacher, he still plays an active part in the school.

Mr Day's daughter Marjorie Townley and son David and his wife Cynthia also attended the event.

Mrs Townley said: "We are delighted about the plaque. It is nice for our family and coming back into the school has brought back wonderful memories."