A Harrow school has had a "sudden shock" closure after an underground chalk mine was discovered under the site showing collapsing tunnels beneath the surface.
Pinner Wood School has been closed until further notice after surveys on Monday (March 20) reported "an unacceptable risk that the ground beneath the school buildings and playgrounds could become unstable and unsafe".
In a joint decision made by governors and Harrow Council, the school was closed on Friday (March 24) and pupils will not return to school in case tunnels running under the site open up new surface holes.
Pupils are not expected to return to the classrooms at an alternative site until the summer term.
Laser imaging from a geo-technical survey team showed previously uncharted and unknown tunnels stretching beneath the school buildings, with mine roofs collapsed in certain places.
Councillor Sachin Shah, leader of Harrow Council said: "With the evidence we have discovered in the past few days, we are certain that this is the right decision.
"We would like to stress that the imminent risk to the school buildings is believed to be small.
"However, the council would never ask or permit any school to operate when there is a known risk, however small, to the safety of the site or the staff and children within it."
Classes will relocate to "other educational settings in Harrow" in time for pupils’ schooling to resume at the start of the summer term according to the council, although specific details are yet to be identified.
Deb Spruce, headteacher of Pinner Wood School, said: "This is a huge and sudden shock to all of us.
"We absolutely need to leave this site until it is made safe.
"Our school is blessed with exceptional staff and governors and a wonderful parent group.
"I’m certain we will all rise to this challenge and show that our outstanding school is united by much more than just our buildings."
The surveys were conducted by Peter Brett Associates and partner Clive Edmonds.
Dr Edmonds said: "It is likely that the mines date from at least the early 1800s.
"As is common for chalk mines of this age there are no mine abandonment plans and the mine workings are in a state of breakdown, as confirmed by the laser survey, posing a hazard to surface stability.
"Our experienced team are purpose-designing suitable investigations to continue to map the workings in order to identify the extent of mining below the school and determine possible remedial options."
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