GKN shares fell 4.8% as the engineering company said its chief executive-designate was to leave the firm.
Kevin Cummings had been due to take over as chief executive on 1 January, but GKN said it felt the next stage of its development was “best delivered under alternative leadership”.
The news came as GKN said it would take a charge of up to £130m at its North American aerospace arm.
Despite GKN’s fall, the FTSE 100 closed up 14.33 points at 7,386.94.
Royal Mail zigzagged during the day but was 1.7% higher at the close. The postal giant reported a 30% fall in half-year pre-tax profits to £77m, although revenues rose 2% to £4.8bn thanks to a strong performance from its Europe-focused parcel business General Logistics Systems.
The company also warned that its performance in the second half of the year, which includes the crucial Christmas trading period, could be affected by the “industrial relations environment” as it tries to reach a deal with unions over workers’ pay and pensions.
On the currency markets, the pound rose 0.18% against the dollar to $1.3196 and was 0.36% higher against the euro at €1.1211