(Close): Advertising giant WPP was the biggest faller on the FTSE 100 on Friday after it gave a cautious outlook for the year ahead.
Its shares fell by 7.95% after it said 2017 had got off to a slow start, citing "tepid economic growth".
The comments overshadowed news of record annual revenues of £14.4bn, which were helped by last year's fall in the value of sterling.
The FTSE 100 closed slightly lower at 7,374.26, a fall of 8 points or 0.11%.
On the FTSE 250, shares in WH Smith closed up 3.36% after Barclays upgraded its rating for the retailer to "overweight" from "equal weight".
Also on the FTSE 250, workwear and hygiene company Berendsen, which had earlier slumped by 17%, finished the day 11.4% lower, after it warned on its 2017 outlook.
The firm reported improved profits and sales for 2016, but said it would struggle with "legacy issues" this year.
On the currency markets, the pound fell after the survey of the UK's dominant service sector added to evidence that the economy has slowed since the start of the year.
The dollar was boosted by expectations of a rise in US interest rates.