No under-55s at this firm

The presence of blood-pressure machines in the pause area of its modern office is the first clue that EverYoung, in Seoul, South Korea, is not your average tech start-up company.

But look more closely at the employees tapping furiously at their computers and EverYoung's unique business model becomes more apparent - the internet content-monitoring company has a strictly ageist policy of employing staff only over the age of 55.

The company, founded by 56-year-old executive Chung Eunsung, aims to address South Korea's demographic time bomb and challenge a corporate culture steeped in age discrimination in favour of the young.

"If seniors are working even after retirement and being globally competitive, then it will be a good solution to our future social problems," he said.

His staff work four-hour shifts, monitoring platforms such as Naver, South Korea's Google equivalent, to censor sensitive information such as a child's identity, on publicly available sites.

Several also conduct coding classes for school pupils.

The oldest worker is 83, and managers praise the workforce for its dedication and for being less addicted to their phones.

Chung does not draw a salary, but pours profits into wages and fringe benefits, including two free annual eye tests, fitness centre membership and a cash bonus for new grandchildren.

Staff are encouraged to exercise or test their blood pressure in the chill-out zone in their hourly 10-minute breaks.

After-work clubs are a pillar of office culture.

Chung wanted to prove that the older generation were easily contribute to Korea's hi-tech-focused economy.

His initial experiment with 30 employees has now expanded to four offices, employing 420.

Amid low birth rates, the over-65s account for 13.2% of South Korea's population, a figure projected to rise to 24.5% by 2030.

His company is now so popular that pensioners compete to join.

Yang Jae-seon, 70, said the job had given him a new lease of life.