The roll call was included in Wednesday's announcement of the deal to create a European trading powerhouse to see off competition from U.S. rivals. But the list would be longer still if it included the lawyers, PR advisers and accountants that will no doubt claim a slice of the fee bonanza.

The 11 banks will be fighting for an estimated fee pot of $85 million, according to Freeman Consulting/Thomson Reuters estimates.

Acting for LSE, Barclays, Goldman Sachs, JPMorgan, RBC Capital Markets, Societe Generale, UBS and boutique Robey Warshaw could share up to $40 million in fees, according to the estimates.

On the Deutsche Boerse side, Perella Weinberg Partners, BofA Merrill Lynch, Deutsche Bank and HSBC will clamor over roughly $45 million.

Lead advisers are likely to take the lion's share of the fees. Many of the banks and advisers named on the roster were added as the deal unfolded. When news of the potential merger first broke, only Robey Warshaw and Perella Weinberg Partners were named as advisers.

Advisory boutique Robey Warshaw is fast becoming the go-to bank for UK Plc. It has advised on three of the largest ever deals involving British companies in the past year.

Deutsche Boerse's main adviser is Andrew Bednar, of fellow boutique Perella Weinberg. Bednar and his firm led the talks for New York Stock Exchange (NYSE) on its ill-fated attempted merger with the German bourse in 2011/12.

UNUSUAL NUMBERS

Even for a potential $30 billion deal, the large number of advisers is unusual.

When Royal Dutch Shell announced its $70 billion takeover of British energy company BG Group in April 2015, only three banks were involved in the transaction.

Nine banks shared the spoils when Glencore took over Xstrata in 2012, while seven handled the merger of Holcim and Lafarge and related asset sales.

That the deal was between financial markets operators could well be a factor, say sources.

"All these banks were brought in at the very end to preserve confidentiality. But they are all important customers, so if we could please them with some league table credits, why not do it?" said one source speaking on condition of anonymity.

And, the deal is not done yet. A takeover battle for LSE could yet ensue.

NYSE owner Intercontinental Exchange has already said it might make a rival bid for LSE, while CME Group is actively considering bidding, people familiar with the matter have told Reuters.

Fee estimates exclude any underwriting or arrangement fees to finance the acquisition. If Deutsche Boerse finances the all-share merger through bonds or loans, it will need to pay between 0.3 percent and 0.8 percent in underwriting/arrangement fees.

(Editing by David Goodman)

By Anjuli Davies and Sophie Sassard