LONDON (Reuters) -Britain's ITV forecast an around 12% jump in advertising revenue in the second quarter, four times the level achieved in the first and ahead of expectations, as it benefits from the Euros soccer championship which kicks off in June.

The company on Thursday reported a 6% drop in total external revenue in the first quarter to 727 million pounds ($908 million), in part reflecting the impact of last year's U.S writers' and actors' strike on its production business.

Chief Executive Carolyn McCall said she expected ITV Studios to be broadly flat over the year, with deliveries such as "Hells Kitchen US" making up the shortfall in the second half.

She said streaming platform ITVX, which saw strong demand for drama "Mr Bates vs The Post Office", delivered double-digit growth in viewing and advertising in the quarter and she expected "continued strong growth in both throughout the year".

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