A PhD student researching assisted dying is suing police for damages over her arrest after travelling with a woman from Wales who had doctors in Switzerland help to end her life.

Miranda Tuckett went to Dignitas in 2022 with Sharon Johnston, a severely disabled 60-year-old from Cardigan in Ceredigion.

She was arrested upon her return to London on suspicion of encouraging suicide, driven to a Dyfed-Powys Police station and held for 11 hours.

The force said it could not comment on a High Court claim of false imprisonment, breach of academic freedoms and assault and battery.

A former pub landlady, Ms Johnston was left tetrapelegic after a falling down a flight of stairs.

She joined several right-to-die groups and six months before her death talked publicly about her plans to pay £14,000 to travel to Switzerland.

Assisted dying is legal in Switzerland for residents and foreign nationals.

Under the law in England and Wales, anyone assisting someone to die or accompanying them abroad to do so can be sentenced to up to 14 years in prison.

Ms Tuckett told the BBC Radio 4 Today programme that she believed the police involved “had a narrative”.

“Did they really have to come to my house… in the middle of the night,” she asked, “and keep me in a cell and take all of my research materials for the best part of six or seven months”.

Dyfed-Powys Police said officers became involved when Ms Johnston was reported missing from an assisted living home.

She got someone to order her a taxi, Ms Tuckett said, and with help from her assisted death chaperone, retired NHS worker Sue Lawford from mid Wales, took phone calls from the police and her care home on the way to the airport.

“She felt quite harassed by those phone calls and told multiple people, multiple times, that she was okay and she’d made her own decision.”

Police in Wales also contacted the authorities in Switzerland, she said, and Swiss officers visited Ms Johnston at Dignitas.

“So you can imagine on the eve of Sharon’s death when she should have been able to reflect on her decision and her life she was fielding calls.”

Ms Lawford was also arrested on her return to the UK.

She has previously called the police response “aggressive”.