Having a strong bond with family, religion and the land will also increase your chances of getting that special birthday card from the monarch, according to the research.

The study of people aged 90 to 101 discovered they shared common psychological traits that gave them better mental health than those up to five decades younger.

Psychiatrist Dr Anna Scelzo said: "We also found this group tended to be domineering, stubborn and needed a sense of control - which can be a desirable trait as they are true to their convictions and care less about what others think.

"This tendency to control the environment suggests noteable grit that is balanced by a need to adapt to changing circumstances."

The characteristics are similar to those displayed at Dunkirk in May 1940 which entered into British folklore - and even today are referred to as the 'Dunkirk spirit'.

Senior author Professor Dilip Jeste MD, a psychiatrist at California University in San Diego, said: "There've been a number of studies on very old adults but they've mostly focused on genetics rather than their mental health or personalities.

"The main themes that emerged from our study - and appear to be the unique features associated with better mental health of this rural population - were positivity, work ethic, stubbornness and a strong bond with family, religion and land."

The findings follow previous studies suggesting hard work is the key to extending life expectancy.Increases in the UK have recently plateaued. The average is currently 79.4 years for men and 83.1 years for women.

But in remote villages in southern Italy - nestled between the Mediterranean Sea and mountains - lives a group of several hundred citizens over the age of 90.

The study published in International Psychogeriatrics found although they had worse physical health their mental state was better than family members aged 51 to 75.

It looked at 29 participants from nine villages in the Cilento region using a set of rating scales for assessing mental and physical health.

These were combined with in-depth interviews to gather their personal stories including subjects such as migrations, traumatic events and beliefs.

Their children or other relatives were also given the same rating scales and asked to describe the personalities of their older relatives.

First author Dr Scelzo, of the Department of Mental Health and Substance Abuse in Chiavarese, Italy, said: "The group's love of their land is a common theme and gives them a purpose in life.

"Most of them are still working in their homes and on the land. They think 'this is my life and I'm not going to give it up.'"

Interview responses also suggested the participants had considerable self-confidence and decision-making skills.

Prof Jeste said: "This paradox of ageing supports the notion well-being and wisdom increase with ageing even though physical health is failing."

One particpant in his 90s told the researchers: "I lost my beloved wife only a month ago and I am very sad for this. We were married for 70 years.

"I was close to her during all of her illness and I have felt very empty after her loss. But thanks to my sons I am now recovering and feeling much better.

"I have four children, ten grandchildren and nine great-grandchildren. I have fought all my life and I am always ready for changes. I think changes bring life and give chances to grow.

"I'm always thinking for the best. There is always a solution in life. This is what my father has taught me: to always face difficulties and hope for the best.

"I am always active. I do not know what stress is. Life is what it is and must be faced - always.

"If I have to say, I feel younger now than when I was young."

The researchers plan to follow the participants with multiple longitudinal assessments and compare biological associations with physical and psychological health.

Prof Jeste said: "Studying the strategies of exceptionally long-lived and lived-well individuals - who not just survive but also thrive and flourish - enhances our understanding of health and functional capacities in all age groups."

Dunkirk was one of the most famous events of the 20th century. Over eight days hundreds of thousands of Allied troops stranded in northern France were rescued by boat and taken back to England.

Some were rescued by military boats while others had to wait for hours - stood shoulder to shoulder in the water, to wait for the flotilla of fishing boats, lifeboats and civilian sail boats hastily assembled by people back in Britain.

The story of the rescue against the odds and the conditions the soldiers were portrayed in Christopher Nolan's film Dunkirk released earlier this year.

People in the UK today still talk of the 'Dunkirk Spirit' which relates to backs-to-the-wall belligerence, solidarity in adversity and a willingness to get through hard times together.

It has even been predicted it will help make Brexit a success.