The Footsie pushed higher as markets largely shrugged off the well-flagged triggering of Article 50.
The FTSE 100 ended the day higher by 30.30 points at 7,373.72, thanks in part to the ease in the pound.
It came after the Prime Minister Theresa May sent a letter to European Council president Donald Tusk, formally triggering the two-year process of UK withdrawal from the European Union.
Neil Wilson, a senior market analyst at ETX Capital said: “The countdown to Brexit has begun but by and large markets shrugged off the triggering of Article 50.
“Stocks and the pound took the momentous decision in their stride, largely as expected as Brexit was already priced in. We might have expected a touch more volatility as the UK delivered the letter but markets were pretty calm.”
The London Stock Exchange Group was one of the biggest risers, up 82p to 3,106p, after European regulators torpedoed its £21 billion merger with Deutsche Borse, saying the two exchanges failed to address competition concerns.
The move comes after the LSE rejected the commission’s request last month to offload its 60 per cent stake in the Italian trading platform MTS.
Mining giant BHP Billiton was close behind, rising 33p to 1,260p, after saying it was well positioned to boost value and returns from its western Australia iron ore operation.
In a contrast of fortunes, travel giant Tui Group sank into the red, down 12p to 1,123p, despite summer holiday bookings meeting expectations.