John Lewis has released an early hint of its Christmas ad with a new campaign centred on its recently revived Never Knowingly Undersold price pledge.

The “through the decades” TV advert is the first in a three-part campaign for the all-important retail ‘golden quarter’, which will culminate with the department store’s highly anticipated Christmas spot.

The first ad features archive footage and focuses on a single store window changing over a century as it is dressed and redressed with products such as fashions of the roaring 1920s and a toaster so innovative that that it took centre stage in 1925.

Scenes are also shown during the outbreak of the Second World War, when the retailer’s Oxford Street store – the first John Lewis – provided a temporary war bunker and was hit during the Blitz on September 18, 84 years ago.

The window recreates the swinging 60s and the 1980s Lycra fitness craze before arriving in the present day with high-tech LED anti-ageing face masks.

The end of the ad features the Never Knowingly Undersold pledge, which began in 1925, reinstated on the shop window.

A still from the John Lewis ad showing its Never Knowingly Undersold pledge on a store window
A still from the John Lewis advert (John Lewis/PA)

The ad’s soundtrack, a version of Paul Simon’s I Know What I Know, is sung by Laura Mvula, while Bafta-winning actress Samantha Morton provides the voiceover.

John Lewis brought back the pledge on September 9 in a major U-turn after ditching the commitment two years ago over concerns it was less relevant to shoppers.

The retailer said sales had “increased significantly” since the pledge’s re-launch, and organic visits to johnlewis.com – or those that are unpaid via search engines – had increased by more than 50,000 a day.

John Lewis customer director Charlotte Lock said: “We’ve looked to our heritage to inform our refreshed value promise to customers, making it relevant for today by matching not only high street retailers but also online competitors – and we are backing it with the biggest marketing campaign in our history.

“We have drawn on our archives and are literally depicting a window on Britain, showing the changing trends and events over the past century.”