Nervous investors sat on their hands waiting on the result of one of the most bitter US presidential elections in modern times.
The FTSE 100 Index edged up 7.2 points to 6814.1 in afternoon trading, with Democrat Hillary Clinton in a slight lead, although polls have tightened towards her Republican rival Donald Trump over the final few days.
In New York the Dow Jones Industrial Average opened 41 points down, or 0.2%, in early trading. Germany's DAX and the Cac 40 in France were also both down slightly.
Spreadex financial analyst Connor Campbell said: "The day only really got duller as it went on, the US open bringing little to the party bar a bit more election anxiety."
In London, Marks & Spencer was the worst performer in the top flight after it said it will cut the number of its clothing and home stores by around 60 in the UK, as it posted an 88% plunge in half year profit.
M&S reported its pre-tax profit tumbled to £25.1m ($31.2m) in the six months to the end of September as sales of clothing and food declined. It also faced a number of restructuring and pensions costs.
In afternoon trading the biggest risers in the FTSE 100 Index were Associated British Foods (+141p to 2630p), BHP Billiton (+26p to 1247.5p), Mediclinic International (+19p to 926p), Randgold Resources (+125p to 6800p) and easyJet (+18.5p to 1013p).
The biggest fallers in the FTSE 100 Index were Marks & Spencer (-14.7p to 334.3p), Imperial Brands (-115.5p to 3687.5p), Barratt Developments (-7.8p to 454.2p), Persimmon (-28p to 1660p) and Glencore (-4.1p to 247.1p).
In afternoon trading the biggest risers in the FTSE 250 Index were Atkins (+27p to 1556p), Tullett Prebon (+6.8p to 402.4p), JD Wetherspoon (+14.5p to 871.5p), Unite Group (+8p to 568p) and Investec (+6p to 504.5p).
The biggest fallers in the FTSE 250 Index were Sports Direct International (-11.1p to 314p), Jardine Lloyd Thompson (-33.5p to 987.5p), Tullow Oil (-8p to 258.2p), Paysafe Group (-12.7p to 417.5p) and JRP Group (-3.2p to 116.7p).