The FTSE 100 index fell from its record high as shares in engineering giant GKN sank after it warned on profits.
GKN fell more than 7% in early trade after it said full-year profits would be only slightly higher than last year.
It blamed "operational challenges" in its North American aerospace business and a £40m charge resulting from "two significant external claims".
GKN was the biggest faller on the FTSE 100, with the index down 26.74 points at 7,529.50.
In the FTSE 250, shares in Provident Financial jumped 14% after the troubled lender said it had put a recovery plan in place for its home credit business.
In August, shares in the company dropped by two-thirds in one day after it issued a profit warning. Provident ran into trouble after an attempt to reorganise its door-to-door lending business failed to work.
On the currency markets, the pound was up 0.35% against the dollar at $1.3311 and 0.45% higher against the euro at €1.1258.
On Thursday, sterling had fallen after the EU's chief negotiator, Michel Barnier said there was still "deadlock" over the Brexit divorce bill.
The fall in sterling helped to push the FTSE 100 to its record closing high. However, the pound then recovered later, with analysts citing a German newspaper report that the UK could be offered a two-year transitional Brexit deal by the EU.