London Stock Exchange boss Xavier Rolet is set to pass a crucial test of his leadership on Tuesday when shareholders back the takeover of clearing house LCH.Clearnet, his first major deal.

LSE and LCH.Clearnet shareholders are expected to ratify Rolet's plan to take up to 60 percent of the clearing operator with an offer of 20 euros per share, which values LCH.Clearnet at 813 million euros (686.2 million pounds).

The partners said on Monday that sufficient LCH shareholders had already voted by proxy in favour of the deal, meaning LSE Chief Executive Rolet needs only the approval of his investors to land the takeover.

Given the very positive share price reaction to the announcement it is unlikely there will be any serious opposition to the LCH deal among LSE shareholders, said Richard Perrott, an analyst at Berenberg Bank.

The LCH deal, expected to complete in the fourth quarter, is seen as crucial for Rolet after his attempt to scoop up Canadian exchange TMX fell through last year after TMX shareholders opposed the deal.

LCH is also strategically important for the LSE as the Anglo-French clearing house will boost its clearing revenue overnight and position the LSE to profit from regulatory changes in the fast-growing market for over-the-counter derivatives.

Clearing houses work to cut the risk of trading on exchanges by guaranteeing each side of the transaction, minimising losses for members if a counterparty goes bust.

This is a great deal for the LSE and executes on Rolet's plan to diversify away from cash equities trading and focus on acquisitions that will deliver higher levels of growth, said Peter Lenardos, an analyst at RBC Capital Markets.

Regulatory authorities in the United States and Europe are keen to introduce as soon as next year rules to force vast swathes of the $700 trillion (436.68 trillion pounds) (436.68 trillion pounds) over-the-counter markets to use clearing, a potentially massive boost for the sector.

LCH.Clearnet's Swapclear is the market-leading service for clearing interest rate swaps, the largest OTC market, and is seen by analysts as a prized asset given the regulatory changes underway.

LCH is perfectly positioned to profit from the regulatory move to force OTC derivatives through central clearing, said Lenardos.

Rolet will be relieved the deal goes through after it was thrown into serious doubt when the planned mega-merger between NYSE Euronext and Deutsche Boerse was blocked by European anti-trust authorities.

NYSE Euronext, which is the largest shareholder and customer of LCH, was seen as a rival bidder for the clearing house and could have scuppered the LSE's move or sparked a bidding war, but Rolet stuck to his guns and a rival bid never emerged.

(Editing by Helen Massy-Beresford)