Blue chip shares struggled for direction as traders waded through the Christmas trading of a flurry of high street traders.
The FTSE 100 Index slipped 13.3 points to 7277.2, as Tesco, Marks & Spencer, Halfords and others posted key festive period performance data. The FTSE 250 Index fell 81.3 points to 18312.8.
Tesco's like-for-like sales lifted 1.5% in the 13 weeks to 26 November year-on-year, buoyed by a strong performance among its fresh food ranges.
During the Christmas period, the six weeks to 7 January, UK like-for-like sales lifted 0.7%, with party food sales jumping by almost a quarter on a year ago.
But shares fell 4.8p to 204.1p with investors seemingly disappointed in its meagre Christmas growth despite a positive picture across the third quarter.
Marks & Spencer's festive trading beat City forecasts led by a strong performance from its under-pressure clothing department as the retailer begins its turnaround.
Same store sales at its fashion and homeware department lifted 2.3% in the 13 weeks to the end of December, well above expectations of a 0.5% rise.
It added group like-for-like sales rose 1.3%, while food sales, which has been the strongest performing part of the business for years, grew by 0.6%.
However, shares fell 2.2p to 338.2p after rising 5% higher in early trading. Spreadex financial analyst Connor Campbell said investors were "perhaps more focusing on the company's tricky bigger picture than the surprising surge in like-for-like sales in its clothing division".
The biggest risers in the FTSE 100 Index were Fresnillo (+63p to 1444p), Randgold Resources (+280p to 6840p), Mondi (+54p to 1704p), Rio Tinto (+107p to 3453p) and Anglo American (+40p to 1325p).
The biggest fallers in the FTSE 100 Index were Associated British Foods (-99p to 2599p), Shire (-165p to 4516.5p), Hikma Pharmaceuticals (-55p to 1849p), Dixons Carphone (-8.6p to 348.4p) and Tesco (-4.8p to 204.1p).
The biggest risers in the FTSE 250 Index were JD Sports (+30.1p to 355.5p), Savills (+54p to 744.5p), Debenhams (+2.5p to 57p), Centamin (+6.5p to 152.1p) and Vedanta Resources (+33.5p to 990.5p).
The biggest fallers in the FTSE 250 Index were Spire Healthcare (-31p to 314.2p), AO World (-14.3p to 170p), Jupiter Fund Management (-26.1p to 419p), Dunelm Group (-36.5p to 760.5p) and Inmarsat (-33.5p to 716p).