The value of the pound slipped as the government said it would officially notify the European Union next Wednesday that the UK is leaving.
The pound slipped 0.4% against the dollar to $1.2344. Against the euro it fell 0.4% to 1.1494 euros.
Meanwhile, the FTSE 100 hit another record, up almost 5 points at 7,429.8.
Dixons Carphone was the biggest riser, adding 2.6%, while insurers Direct Line and Admiral both rose about 1.7%.
Associated British Foods also gained 1.7% as Goldman Sachs improved its rating on the Primark owner to “buy” from “neutral”.
Royal Bank of Scotland was the biggest faller, shedding 1.6%.
Dafydd Davies, partner at Charles Hanover Investments, said: “The financial stocks have all been on a pretty good push over recent sessions, so we are starting to see some short-term profit-taking come in.
“We could start to see, as Brexit uncertainty builds, a bit more de-risking on the financials that are particularly exposed to the direct state of affairs in question.”
“The pound dropped sharply after we received the news that traders have been waiting for – Theresa May will trigger Article 50 next week,” said Neil Wilson at ETX Capital.
“Despite the fact it’s a known quantity we have to assume that the stark reality of exiting the European Union is hitting home.”
Vodafone investors were unmoved by news that it had merged its Indian mobile business with Cellular, India’s third-largest network, to will create the company’s biggest operator. Vodafone’s shares inched down 0.3% to 210.6p.