A London theatre has been fined after an Australian woman was left paralysed when she fell through a so-called Juliet door that opened into thin air.

Rachael Presdee was left a paraplegic when she fell three metres to the stage floor in the June 2012 incident.

The Soho Theatre Company on Monday was fined STG20,000 ($A36,500) and ordered to pay STG10,000 ($A18,250) in costs after previously admitting health and safety breaches.

Ms Presdee, 38, has separately settled a civil claim with the theatre.

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"We have done as much as we can to ensure that Rachael received the best possible care after the accident and we are relieved for her that her civil claim has now been settled," the not-for-profit company said in a statement.

It was revealed last week the Australian was awarded STG3.7 million ($A6.8 million) in one of the biggest out-of-court payouts in the UK entertainment sector.

In a statement issued through her union, Equity, Ms Presdee said: "I could not have imagined when I walked into work on June 9, 2012 that I would never walk out of there, or walk anywhere else ever again."

Ms Presdee was working as a stage manager on a production of Boys for the Headlong theatre company when the accident happened at the Soho theatre.

Judge Alistair McCreath on Monday described her injuries as "catastrophic".

"One only has to read her two victim impact statements to see the way in which, and the extent to which, her life has been turned upside down," he said.

"She is now a wheelchair user. She has suffered devastating life-changing consequences which have had a fundamental effect on her whole way of life.

"She has met that challenge with great courage and very strong determination."

Ms Presdee returned to Australia after the accident.

The judge said the Juliet door presented a risk which was "obvious and known and had become increasingly higher over time".

"This was a serious breach of the duty of the company to assess risk and to protect people at its premises from risk."

Ms Presdee arrived at the theatre on the day of the accident to find the lights off and the auditorium shrouded in darkness.

She climbed a spiral staircase looking for the light switch when she found an unmarked and unlocked door.

Hidden behind it was a balcony used in Romeo and Juliet. She opened the door and plummeted three metres on to the stage below suffering severe injuries.

The balcony and door once had a lock and bar across it to protect people from falling but these had been removed.