Comcast Corp. (CMCSA) shares slumped lower Monday after the biggest U.S. cable group topped rivals Walt Disney Co. (DIS) and 21st Century Fox (FOXA) for the right to buy Britain's Sky Plc  (SKYAY)  but may struggle to convince shareholders to cash-in on the near $40 billion offer.

Comcast bid £17.28 per Sky share in the third and ultimate round of bidding of a rare two-day auction conducted by the U.K. takeover panel in London, a figure that values Sky at more than £30.2 billion ($39.5 billion). However, with Disney set to hold a 39% stake in Sky following its $71.3 billion takeover of Fox, and activist shareholders such as Elliot Management perhaps content to hold onto their investments, Comcast could be stuck between paying a high price for Sky but not having complete control over Europe's biggest pay TV broadcaster, despite a ringing endorsement from the target.

"It is in the best interests of all Sky Shareholders to accept the (Comcast offer)," Sky said Monday. "Accordingly, the Sky Independent Committee unanimously recommends that Sky Shareholders accept the (Comcast offer), and in order to ensure the successful closing, and given the possibility of a delisting of Sky in the near future, urges shareholders to accept immediately."

Comcast shares were marked 7.8% lower in New York Monday to change hands at $34.97 each, a move that extends the stock's year-to-date decline to around 13%. Sky shares, meanwhile, were a notable early mover in London, rising rising 8.77% to trade at £17.24 each following Saturday's sealed-bidding auction.

Comcast CEO Britain Roberts called the win a "great day" for the Philadelphia-based group, adding that Sky is a "wonderful company with a great platform, tremendous brand, and accomplished management team."

"This acquisition will allow us to quickly, efficiently and meaningfully increase our customer base and expand internationally" he added. "We couldn't be more excited by the opportunities in front of us. We now encourage Sky shareholders to accept our offer, which we look forward to completing before the end of October 2018."

Fox, however, declined to comment on what it intends to do with its 39% stake in Sky -- now valued at $15 billion based on the Comcast bid -- which will transfer to Disney once its sale of media-assets with the House of Mouse is closed next year. 

Comcast, which owns both NBC network and Universal Pictures, will also need to convince its existing shareholders that its £17.28 per share bid -- which is more than 125% higher than Sky's market value prior to Fox's first attempt to buy it in 2016 -- wasn't too far of a reach for a group with a mid-tier investment grade credit rating of A3 by Moody's Investors Service.

The European media sector is also undergoing major changes, with Italy's Mediaset, the nation's biggest private broadcaster, hinting earlier this month that they're "working on something big and something complex", according to CEO Pier Silvio Berlusconi, following its failed takeover of France's Vivendi.

Disney/Fox also has the option of holding on to its stake even if Comcast prevails, a tactic which would allow it to wait-out changes in the global streaming and media landscape, particularly following next year's EU exit by the United Kingdom and the evolving regulations on data privacy and media hegemony from both London and Brussels.

Disney/Fox, along with activists who've booked some pretty solid gains and are playing with house money -- Sky has risen some 58.3% since the start of the year -- couldn't be blamed for wanting to watch those developments unfold before cashing out.

Activist investor Crispin Odey, who founded Odey Asset Management, had said he thought the bidding could reach £18 a share, a price that would value the group at £50 billion ($66 billion).

France's Vivendi SA (VIVHY) , which owns Universal Music Group and the Canal+ pay-TV network, was marked 1% higher at €22.28 each in Paris Monday. Italy's Mediaset, the nation's biggest private broadcaster, was marked 0.5% higher at €2.64 each.

However, the Comcast victory also scuppers Disney's plans to rollout a global streaming service for its digital content to take on rival Netflix Inc. (NFLX) , which last week unveiled a tie-up with Sky called 'Ultimate on Demand'.

Sky has around 23 million customers across five European countries, including the United Kingdom, and would have been a significant launch pad for Disney's international ambitions.

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