LONDON (Reuters) - British department store John Lewis is reintroducing its 100-year old "Never Knowingly Undersold" promise for customers on Monday, two years after it dropped it, hoping a revamped version of the price guarantee will help drive growth.

The employee-owned retailer, which also operates Waitrose supermarkets, returned to annual profit in March after three difficult years, and the new head of its department stores hopes the commitment to value will boost revenue.

"It gets us back on the front foot," executive director Peter Ruis told reporters on Thursday.

John Lewis has struggled in recent years after investing heavily to compete with online rivals at a time when a cost-of-living crisis has affected the incomes of its typically more affluent customers.

But a turnaround effort is already underway, ahead of former Tesco executive Jason Tarry joining in mid-September as its new chair before incumbent Sharon White steps down.

Ruis said removing the price promise had caused customers to believe John Lewis had become more expensive.

Under the refreshed pledge, John Lewis will match prices on branded goods with 25 online and high street retailers including Amazon, Apple, Argos and rival department store House of Fraser.

If customers find the same product more cheaply elsewhere within seven days they can claim the difference back.

The cherished "Never Knowingly Undersold" mantra, a well-known feature of shopping at John Lewis since 1925, was scrapped in 2022 after it became too complicated and costly.

But Ruis said AI technology enabled the retailer to bring back an important part of its heritage, a move he hopes will draw in shoppers, particularly in beauty and technology.

He expects the return of the promise, accompanied by a multi-million pound marketing campaign, will bring "significant upside" to sales, but it was too early to say by how much.