UPDATE:  ROME — The Brexit vote rattled European markets Friday, with media stocks among the hardest hit and the pound plunging to its lowest level in 30 years.

London’s FTSE 100, which was down 4.47% at midday, subsequently picked up to close at minus 2.8%. But London’s FTSE 250 index, which is more focused on British companies and thus more representative of the U.K. economy, ended the day down 7.19%, its steepest fall since since the so-called Black Monday crash in 1987.

Meanwhile, the Milan bourse closed down 12.48%, its worse tumble in more than a decade. And the Madrid stock index suffered a more than 12% loss.

By closing of trading Friday, the Euro Stoxx 600 Media index had plunged by 7.5%. Private British TV broadcaster ITV lost more than 20% because of fears that advertisers would be pulling back. ITV chief executive Adam Crozier said in an email to staff that there would “clearly be some short-term uncertainty.” His email was posted on Twitter.

Italy’s Mediaset, owned by former Prime Minister Silvio Berlusconi, closed down 17.17%, France’s Vivendi dropped 6.25% and Murdoch-owned pan-European pay-TV Sky lost 6.6%. German conglomerate ProSiebenSat shedded 7.38%. Entertainment One, the international company that operates in Canada, the U.S., and the U.K., among other countries, ended the day down 19.2%.

International currency fluctuations have already been a drag on the earnings for the largest media conglomerates in the past two years. The promise of more volatility ahead is unwelcome news for U.S.-based companies that are increasingly banking on overseas growth to drive future earnings.