The UK's FTSE 100 index closed at its lowest level for the year, slipping below 7,100 points after sterling rose against the dollar.
(Close) Talk Talk was the biggest winner on the London stock market after chief executive Dido Harding announced she would be stepping down.
The benchmark share index dropped 19 points, or 0.3%, at 7,099.
Shares in the telecoms group finished 7.6% higher on the FTSE 250, as it also announced founder Sir Charles Dunstone would become executive chairman.
Earlier this month, the FTSE reached a record closing high of 7,327 after a 15-day winning streak, but has since given up all of this year's gains.
Meanwhile, the benchmark FTSE 100 index crept back above 7,100 points, helped by drugmaker Hikma Pharmaceuticals.
In part that has been due to a rally in the pound, and sterling rose again on Tuesday against the dollar.
Hikma shares rose 3.1% after President Trump met with the drugs industry.
The FTSE 100 is made up of a large number of companies which make most of their profits outside the UK, and so benefit from a weaker pound.
The US president told executives of major US drugmakers in a White House meeting on Tuesday that he would work with pharmaceutical firms to lower drug prices.
'Even rockier'
The FTSE 100 closed 8.5 points, or 0.1%, higher at 7,107.65.
Sterling was 0.7% higher against the dollar at $1.26 amid uncertainty among investors over the policies of the Trump administration.
"The FTSE 100 has lagged behind somewhat probably as a result of the strength of the pound," said Michael Hewson, chief market analyst at CMC Markets UK.
Michael Hewson, chief market analyst at CMC Markets UK, said: "The events of the last 24 hours and the departure of the US Attorney General have served to build up that apprehension and the risks that the investment road could well start to get even rockier with even more potholes."
The pound rose 0.5% against the dollar at $1.2638, and 0.9% against the euro at 1.175 euros, after a survey indicated UK manufacturing output remained near a two-and-a-half year high.
The pound fell 0.2% against the euro at 1.166, after the euro was boosted by the release of a raft of economic data that suggested the bloc's recovery was picking up pace.
Among individual shares in London, Ocado jumped nearly 10% after the online grocer reported a rise in full-year profits, before paring those gains to finish 2% higher.
The company reported a 22% increase in pre-tax profits to £14.5m for the year to 27 November.
Also in the FTSE 250, Britvic shares were up 6% after the soft drinks company reported a rise in first-quarter revenues.
