The FTSE 100 jumped amid global trade optimism while the pound wobbled amid fears of the potential for a hung parliament in a volatile trading session.
London's top flight closed 57.22 points higher at 7,273.4 at the end of trading on Thursday.
Both currency and equity traders started the session cautiously, but the markets were given a shot in the arm in the afternoon session by President Donald Trump.
Michael Hewson, chief market analyst at CMC markets UK, said: "Caution lasted until just after the US open when President Trump tweeted that a "BIG DEAL" with China was getting very close.
"This of course had the wholly intended effect of juicing the markets higher, sending the FTSE100 to one-week highs, and markets across Europe higher in general."
The London markets all closed higher as they were also boosted by weakness in the pound, which was nervy as voters went to the polls.
Connor Campbell, financial analyst at Spreadex, said: "With the Telegraph's final poll suggesting the Tory lead has shrunk to just five points, putting the result of the election in potential hung parliament territory, the pound had a notable wobble."
The value of the pound decreased 0.37% versus the US dollar at 1.312 and dipped 0.66% against the euro at 1.181.
The major European markets also welcomed the US president's positive exclamations, as traders hope an initial deal can be placed before the US slaps planned tariffs on Chinese goods.
The German Dax increased by 0.73% while the French Cac moved 0.59% higher.
Across the Atlantic, the Dow Jones also pushed higher, shooting up by 300 points to hit an all-time high for the US index.
In company news, shares in Ocado nudged higher after the company said it saw a surge in customers searching for vegan and gluten-free Christmas options as it reported a jump in sales.
The company also said plans to launch Marks & Spencer products on its site from September are progressing well and recent surveys show customers are warming to the new plans.
Shares in the business closed 12.5p higher at 1,210p at the close of play.
Superdry shares fell as the retailer posted an 11% fall in sales to £369.1 million and swung to a pre-tax loss of £4.2 million for the six months to October 26.
Meanwhile, the company's founder vowed to stay with the business until at least April 2021 as he works through his turnaround plans following a boardroom coup earlier this year. Shares dropped by 17.4p to 482.6p.
Dixons Carphone leapt higher as the retailer said it is on track for turnaround despite posting significant losses in its UK and Ireland business.
Shares in the phone and electronics retailer rose 9.3p to 141.25p.
The price of oil increased as it was helped by a favourable outlook from the US Federal Reserve on Wednesday as well as positive comments from the European Central bank.
The price of a barrel of Brent crude oil rose by 0.75% to 64.34 US dollars.
The biggest risers on the FTSE 100 were M&G, up 10.8p at 229.8p, Evraz, up 16.1p at 369.5p, Standard Chartered, up 26.8p at 718p, and Prudential, up 50.5p at 1,369p.
The biggest fallers on the index were Severn Trent, down 66p at 2,221p, United Utilities, down 24.4p at 848.4p, Hikma, down 48p at 1,928p, and Ferguson, down 150p at 6,650p.
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