LONDON, July 28 (Reuters) - Britain"s ITV (ITV.L) said advertising had rebounded strongly, with June delivering the largest ad revenue for the month in the broadcaster"s history as it benefited from the easing of COVID-19 restrictions and the Euros. The company, which broadcast England"s semi-final victory over Denmark in Euro 2020 to a peak of 27.6 million people this month, said external revenue for the first half rose 27% to 1.55 billion pounds ($2.15 billion), beating analyst expectations. Chief Executive Carolyn McCall said ITV was emerging from the worst effects of the pandemic. "We are optimistic about the future, despite the ongoing pandemic risk on our advertising and ITV Studios revenues," she said on Wednesday. Underlining the strength of the recovery, ITV said total ad revenue for June and July was expected to be 16% higher than the same period in 2018, when it broadcast the Football World Cup and series 4 of its smash hit "Love Island". "For us to have such a strong rebound in advertising every category has performed, except travel," McCall told reporters. She said June has "just been a fantastic month", with the Euros the most successful tournament ever for ITV. "I hope it"s something that we just build on and go from strength to strength," she said. ITV said ad comparatives become tougher in the second half, but it expected July to be up 68%, August up 17% and September to be positive. Shares in ITV, which have doubled in the last 12 months, were trading up 0.5% at 120 pence, as analysts at Citi said the company had delivered a solid beat, with "clearly undeniable" strength in ad revenue. McCall said ITV would restart a progressive dividend policy based on a notional dividend of 5 pence a share, with a first payout of 3.3 pence proposed at the full year. First-half adjusted core earnings nearly doubled to 327 million pounds, it said, driven by the ad recovery, resumption of production in its studio business and cost control. ($1 = 0.7210 pounds)