Sainsbury's was the cheapest major supermarket in the final month of 2019, with a trolley of 71 popular branded groceries costing £139.86.
If you were shopping at Waitrose, you would have paid £160.87 - a massive £21.01 more - for exactly the same items. This makes Waitrose the priciest supermarket in the UK for the 10th month in 2019.
However, Ocado was barely any cheaper, at £160.26.
Asda was the second-cheapest supermarket, with the trolley costing £141.64, followed by Morrisons at £149.84.
Shoppers at Tesco, once known for its value, would have paid £158.37 for the same basket of groceries - putting it just behind higher-end Waitrose and Ocado.
Using data from independent price comparison site MySupermarket.co.uk, we calculate the average price (including special offers but not multibuys) for a trolley of popular branded items.
In December, we tracked the prices of 71 popular items, including Andrex Classic Clean white toilet rolls, Fairy Non Biological washing powder, Hovis Soft White medium sliced bread, McVitie's Ginger Nuts, and Tetley teabags.
The links below take you to our reviews of each supermarket.
Supermarkets took a record £29.3 billion through tills during the 2019 silly season, according to consumer insight company Kantar.
While grocery sales grew marginally year-on-year, up 0.2% in the 12 weeks to 29 December, it wasn't all festive cheer for the supermarkets: this increase represents the slowest growth rate since 2015. Both average household spending and volume sales fell compared with 2018.
Sales of Christmas puddings were down by 16%, while seasonal biscuits were 11% lower. Shoppers also popped fewer corks this year, as sparkling wine sales dipped by 8%. Sales of beer were up 1%, and still wine sales were up 2% compared with Christmas 2018.
The big four supermarkets - Asda, Morrisons, Sainsbury's and Tesco - all posted small losses year-on-year, but German discounters Aldi and Lidl experienced a bumper festive period.
Lidl led the way with sales growth of 10.3% over the past 12 weeks and increased its market share, too. Together with Aldi, the discount retailers took their highest-ever combined Christmas market share.