Every time Aldi features as a guest retailer in the Grocer 33 it wins big - and this was no exception.

The discounter’s £43.50 total was £7.82 or 15.2% cheaper than second-placed Asda, which represents a slight increase from the 15.1% it achieved in its previous guest slot in May.

Aldi offered the cheapest price on 32 of the 33 items, and was exclusively cheapest on 27 (the only item cheaper elsewhere was a four-pack of baking potatoes at Morrisons, on a half-price deal at 50p this week).

True, Asda (and others) matched Aldi or ran it close on some items, but it was 35% cheaper on the streaky bacon, despite the price having risen by 24p in the last year (see right) and the Douwe Egberts coffee was 35% cheaper also, while the cauliflower, cream, flour and both melons were all around 20% cheaper or more.

Best of the rest Asda also scooped the service and availability prize this week, reflecting its current strategy, which is as focused on improving the customer experience as it is on competitive pricing. Its £51.32 total was £1.08 cheaper than third-placed Tesco. This was reduced to just 49p after our Tesco shopper received an instant 59p cashback via its Brand Guarantee initiative.

Asda did have to dish out a voucher for £3.82 to our shopper as part of its own Price Guarantee scheme, which was based on a comparison with Morrisons, though it also failed to meet its stated aim of being 10% cheaper than Tesco and Sainsbury’s as well.

Morrisons, second last week, was relegated to fourth, with its £53.13 total £9.63 more expensive than Aldi, a difference of 18.1%. Sainsbury’s, was over a tenner more expensive at £53.86. And, as expected, Waitrose came last. Aldi was a meaty £16.84 cheaper, a margin of 27.9%, with its streaky bacon well over double the price.