The Flash: How Knebworth House doubled for America

Ezra Miller was on set at Knebworth House, where the actor was described as "very quiet"

A stately home's grounds have been transformed into a US suburb for a new DC superhero film from Warner Bros.

Knebworth House's estate was used as a filming location in The Flash, starring Ezra Miller.

Production crews built a life-sized American street which required a gardener, and planning permission from North Hertfordshire District council.

Trish Washer, operations manager at Knebworth, said "it looked like it had been there forever".

A smoke machine was used to transform Hertfordshire into Gotham City

Between an avenue of oak trees, planted in 1887 for Queen Victoria's Golden Jubilee, production teams built five houses complete with front gardens, and a road featuring fire hydrants and zebra crossings.

Mrs Washer said: "In America the streets are huge with big houses amongst big trees.

"Rather than bringing trees in at a large expense into a field, the avenue of trees was wide enough for them to build a street and houses within those trees."

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Although only one of the houses had a decorated interior, Warner Bros hired a dedicated gardener to tend to the gardens of all five houses so the gardens looked "lived in".

"They brought in loads of shrubs, plants and bits and pieces to make it look authentic," she said.

"Because the trees are so well established, they hung over the houses as if they'd always been there."

Knebworth House, just outside Stevenage, is a popular filming location because there are many nearby film studios

Mrs Washer praised Warner Bros who invited local residents to visit the set for refreshments and to answer questions.

When filming was complete, crews spent months carefully restoring the grounds of the privately-owned estate to the condition they found them in.

Anything the studio did not take with them was given to Knebworth House to recycle or reuse, including turf that ended up in the wilderness area of the garden.

Knebworth House previously featured in Tim Burton's version of Batman, released in 1989

Ezra Miller was on set at Knebworth House where they were described as "very quiet"

Filming also took place at the gatehouse which has also featured as Wayne Manor in Tim Burton's 1989 version of Batman.

As Michael Keaton has returned to play Batman in The Flash, film crews wanted to use Knebworth as his home once again.

Lead actor Ezra Miller passed through the gates in a yellow US-style taxi surrounded by thick fog from a smoke machine.

"We had to have a spotter for that on the A1 so that it doesn't drift, obviously with the A1 being in close proximity to Knebworth," said Mrs Washer.

She said she was very impressed by the production team, made up of nearly 300 people.

"The attention to detail, the creativity and the workmanship was just phenomenal," she said.

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