John Lewis sales soared 15.3% to £70.51m in the week to September 1 as “the first signs of autumn” drove footfall.

The department store group enjoyed a strong back to school week, particularly over the Bank Holiday weekend in categories including fashion and technology.

In the latter category, sales of tablets “remains the stand-out result” while trade in white goods and small electrical products remained strong, according to Chris Hooper, head of operational support at John Lewis.

Hooper added that online sales enjoyed a “significant upward shift in performance”, soaring 36%.

In the week, the retailer launched its House by John Lewis own brand. Hooper said the retailer  was pleased with the early response to the “modern and uncluttered” home range.

Since the period end, the retailer this week launched its exclusive new fashion range Somerset, designed by Alice Temperley. Hooper called the collection a “really exciting collaboration for the Fashion team”.

John Lewis also this week opened its first ever pop up shop in Exeter, ahead of its flexible format department store opening next month.

The best performing stores in the estate were Southampton and Reading. The John Lewis at home shops in Poole, Croydon and Swindon also performed strongly.

At sister chain Waitrose sales were up 6.4% to £105.41m as Brits stocked up their cupboards and freezers as they prepared to go back to school or work.

Frozen pizzas were up 14% while frozen vegetables grew 11%. The sunshine in the week also boosted barbecue sales, with meat sales up 29%.

World beers and speciality beers increased 24% and 46% respectively.

Online grocery sales surged 50% as customers opted to “enjoy the rest of their time off in the comfort of their home”, according to Rupert Thomas, marketing director at Waitrose.