The agency was brought in after Carrousel's approach included a demand for representation on the board of Gartmore European Investment Trust.
Carrousel owns just under a third of the Roger Guy-managed firm's shares. It wanted to appoint three of its representatives to the Gartmore board, effectively gaining control of the trust.
Lansons' brief is to ensure high shareholder turnout at an upcoming vote. It needs support from more than half of shareholders - the normal turnout for shareholder meetings is ten per cent.