'I leave in tears': Sir Jackie Stewart on the heartbreak of his wife's dementia battle

Motor racing legend Sir Jackie Stewart has opened up on his wife’s battle with dementia, recounting the first time she forgot who he was as he described the changes in behaviour he had witness as “horrendous”.

Sir Jackie Stewart and his wife Helen following the funeral of Justin Wilson at St James the Great Church in Northamptonshire in 2015 | PA

The three-times F1 champion, who was born in Milton, Dunbartonshire, spoke as his charity Race Against Dementia started funding a new dementia blood test.

The blood test trial being developed by the University of Cambridge aims to detect signs of frontotemporal dementia up to 20 years before the disease is diagnosed.

Speaking about the battle against dementia, Sir Jackie recalled the moment when Lady Helen asked "where's Jackie?" while sitting next to him.

His wife of 60 years was diagnosed with dementia after a car accident a decade ago in which she lost control and the vehicle flipped onto its roof.

Sir Jackie said told the BBC: "Just the other day it was time for dinner, she's [my wife] getting up and I'm sitting close by, and she says 'where's Jackie?' That's the first time that's happened and that's only a few weeks ago ... a bad feeling came over me.”

Sir Jackie, who now lives in Buckinghamshire, said the disease’s progression meant his wife could no longer walk.

Sir Jackie Stewart photographed at home in August 2013 | Andrew O'Brien

"I know that Helen doesn't mean it when she suddenly goes round and hits me, or the [specialist dementia] nurses," he said.

"She can hit somebody quite often. She uses language that she's never ever said in her life and it comes like that [clicks his fingers] and I say 'darling, darling, don't say that'.

"She says 'why?' And she'll give me a row for doing that. That's usually after 5pm."

Sir Jackie Stewart and his wife Helen attending the wedding of Spice Girl Geri Halliwell and Formula 1 boss Christian Horner at St Mary's Church in Woburn, Bedfordshire, in 2015 | PA

Sir Jackie launched the Race Against Dementia campaign to find a cure for the disease after his wife was diagnosed with the degenerative condition.

A characteristics of the condition is referred to as “sundowning”, where a person - like in Lady Helen’s case - will behave in ways that are difficult to understand in the late afternoon or early evening.

An accessible home has been created in Switzerland for Lady Helen, where she is cared for by nurses and specialist neurosurgeons. But Sir Jackie acknowledged while his F1 career had afforded him the opportunity to set up the home for his wife, most families only had the option of placing loved ones suffering from dementia into residential care.

"I visit homes for people with dementia and I leave in tears because people are completely lost," he said.

The F1 legend said he hoped a cure could be found in his lifetime. One in three people develop dementia in their lifetime, according to the Alzheimer’s Society.

"I want this [a cure] to happen just as much as I wanted to be world champion," Sir Jackie said. "It's terribly important."

Dr Maura Malpetti, senior research fellow at the University of Cambridge, said the the ON-FIRE study was looking into the forms of frontotemporal dementia that were not genetic. She said there was a frequent problem with people being misdiagnosed.

The trial will eventually be rolled out to 1,000 participants, with 300 patients initially being recruited across England.

"It is confused with psychiatric conditions because of the behavioural changes or the language problems," Dr Malpetti told the BBC.

She added: "I think there's been a revelation in the field of blood tests because this allows us to use more accessible and scalable tests.”