The FTSE 100 added 0.7%, helped by a 12% surge in travel company TUI after it said strong demand for holidays would help offset a hit from the Boeing 737 MAX aircraft groundings on its annual profit.
Airlines easyJet and British Airways-owner IAG also added roughly 4% each.
The mid-cap FTSE 250 rose 0.7%, helped by a 7% jump in William Hill after the bookmaker announced a partnership with U.S.-based CBS Sports.
Fed chief Powell remained fairly upbeat about the outlook for the U.S. economy, though he warned the coronavirus could lead to disruptions in China that spill over to the rest of the global economy.
"The global stock market rally is being powered by central banks and, with a lot of the January and February data being tossed out the window, risk appetite may run wild for a few more weeks," OANDA analyst Edward Moya said.
"The People's Bank of China will remain active in delivering more easing and with the Fed possibly on standby, risky assets could remain attractive in the short-term."
Britain's benchmark stock indexes have mirrored volatile swings in global markets over the past few weeks as the China-linked virus spreads, raising concerns about a widespread hit to economic growth.
The death toll from the outbreak has now crossed 1,000 but investors drew some comfort from signs from a slowdown in new cases in Hubei province as well as the steps Beijing has taken to pump more cash into the economy.
After soaring more than 30% in the previous session, shares in NMC Health gave up half those gains as private equity firm KKR said it did not intend to make an offer for the healthcare provider.
Intu Properties handed back almost all its advances from Monday and tanked nearly 30% to a fresh life low after saying Hong Kong-based Link REIT would not participate in its cash raise.
(Reporting by Shashwat Awasthi in Bengaluru Editing by Patrick Graham/Mark Heinrich)
By Shashwat Awasthi