The latest episode of long-running medical drama Casualty will be entirely improvised to reflect the pressure faced by NHS staff.

John Sen, executive producer of the Cardiff-based show, said it allowed the show to portray the "authentic experience" of ambulance workers.

"We are all aware of the pressures that the NHS is facing at the moment... and so we wanted to reflect that," he said.

Casualty actor Michael Stevenson said the cast had "no idea what they would be faced with" and did not meet any of the guest actors before the shoot.

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