The headteacher of an Oxford is determined that a rare weed that halted the building of a new classroom a year ago will not stop plans to take in an extra 50 pupils.

Contractors stopped work last October when they discovered Japanese Knotweed on land opposite New Hinksey School in Vicarage Road, south Oxford.

The land at the back of St John's Church is owned by the Oxford Diocese, which has agreed to lease it to Oxfordshire County Council so the school can expand.

The church hall was to be demolished to make way for a new nursery class.

As part of the reorganisation of Oxford schools, New Hinksey is becoming a primary school catering for 150 children aged up to 11, and a new classroom is essential.

But the weed was discovered the day contractors began building last October.

The plant, introduced to England in the 19th century, is so strong it can burrow under buildings and eat into the foundations. Work was stopped immediately.

New plans are to be submitted to Oxford City Council to develop a new playground instead on the land surrounding the 30ft wide patch.

Meanwhile the weed will be treated with herbicide for five years in the hope of eventually killing it.

If permission is given, a new classroom will be built beside the existing school buildings on the other side of the road to the church, on part of the school's existing playground.

Headteacher Jenny Lee said the new plan was equally exciting.

She said: "It will be a real asset. This will give us more playground space on the Diocesan land.

"A new classroom is essential for us to become a primary school and take these additional children.

"The new building has been designed to blend in with the original Victorian building with the same pitched roof and same colour bricks.

"We expect to be able to use the play area next summer.

"The work won't take as long as the planning application process."

Oxford City Council planners are due to discuss the application in December and the school hopes building work will begin in March.