Sterling weakened on a warning from Chancellor Phillip Hammond that flights could be grounded in the UK if no deal was sealed before leaving the European Union.
Despite the decline in the value of the pound, the FTSE remained flat at 7,532 thanks to a continued underperformance from the banking sector.
Lloyds (LLOY) led the sector lower, down 0.8% to 66.4p. Royal Bank of Scotland and HSBC (HSBA) both dipped 0.8% and 0.6%.
Brent crude oil fell 0.6% to $56.22 per barrel. Gold declined 0.3% to $1,286 per ounce and copper climbed 0.6% to $3.06 per pound.
Investor sentiment was cautious in the US on Wednesday as the market waited for several banks to report their third quarter earnings. The S&P 500 was flat at 2,551.
MID AND LARGE CAP RISERS AND FALLERS
Media reports suggested that activist hedge fund Elliot Management is building a stake in medical device maker Smith & Nephew (SN.), which gained 3% to £14. At last year's annual shareholder meeting, there was a shareholder rebellion, which implies a good opportunity for Elliot to enter the firm.
Home furnishings retailer Dunelm (DNLM) enjoyed a 6.2% lift in its shares as first-quarter like-for-like sales increased 9.3%, despite some margin contraction.
Packaging firm Mondi (MNDI) disappointed the market after warning its performance for the full year would be modestly below market expectations, causing the stock to deflate 7.8% to £19.26.
New business at wealth manager Hargreaves Lansdown (HL.) helped its assets under administration rise by 4% and boosted third quarter sales by 15%, but this failed to spark the share price at £14.96.
A poor performance in the UK hit recruitment consultancy PageGroup (PAGE) as its shares slumped 9.2% to 477.1p. Investors overlooked an 11.8% rise in third-quarter profit, driven by strong results abroad.
A £9m contract with Heathrow Airport for defence firm Ultra Electronics (ULE) failed to move the stock at £18.33.
Countryside Properties (CSP) was up 0.3% at 349.2p despite completions increasing 28% to 3,389 homes in the year to the end of September 2017.
SMALL CAP RISERS AND FALLERS
Maiden results from fashion retailer Quiz (QUIZ) got short shrift despite the fact revenue was up 35% in the six months to 30 September. Investors were disappointed by a lack of earnings upgrades as the stock fell 2.4% to 182.4p.
Property developer Telford Homes (TEF) warned its pre-tax profit for the first half of 2018 will be significantly lower than the second half thanks to the timing of certain projects, causing its shares to decline 2.3% to 398.7p.
News that Alpha Returns Group (ARGP) needed a new nominated adviser by 20 November to avoid being kicked off AIM wiped over a fifth off the firm's value.