Shares in Barclays were the biggest fallers on the FTSE 100, despite the bank reporting a doubling of quarterly profits.
Pre-tax profit for the first three months of the year jumped to £1.682bn, from £793m a year earlier.
But analysts were disappointed by the performance of Barclays’ investment bank, and the shares fell 5%.
Shortly before midday, the FTSE 100 index was down 19.80 points, or 0.3%, at 7,217.57.
Shares in Royal Bank of Scotland were having a better day, rising 1.7%, after it reported its first quarterly profit since third quarter of 2015.
RBS posted profits of £259m in the first three months of 2017, compared with a £968m loss a year earlier.
Rising copper prices boosted shares in mining companies, with Antofagasta, BHP Billiton and Rio Tinto all up by more than 2%.
In the FTSE 250, shares in transport group Stagecoach fell 3.25% after HSBC cut its rating on the company to “reduce” from “hold”.
On the currency markets, the pound shrugged off weaker-than-forecast UK growth data. The UK grew by 0.3% in the first quarter of the year, according to an initial estimate, a sharper-than-expected slowdown from the 0.7% rate seen at the end of 2016.
Despite this, the pound continued to rally against the US dollar, hitting a fresh seven-month high of $1.2951 at one point.
However, sterling was lower against the euro, down 0.3% at 1.1837 euros. The euro was boosted by the latest set of eurozone inflation figures, which indicated that inflation in the 19-nation bloc rose to 1.9% in April.