College Hill has been called in on a project basis and is working on the deal alongside Execution Noble's retained advisers Cubitt Consulting.
BESI will acquire a 50.1 per cent stake in the firm for an undisclosed sum.
The combined group, which will particularly target emerging markets such as Brazil and India, will have a 1,000-strong team operating from 13 offices worldwide.
Execution Noble was only officially formed earlier this month after approval from the FSA, following the merger of Execution Holdings and Noble Group Holdings, announced last December.
Portuguese investment bank Banco Espirito Santo de Investimento calls in College Hill
Banco Espirito Santo de Investimento (BESI), Portugal's largest investment bank, has brought in College Hill to advise on its acquisition of a majority stake in UK-based investment bank Execution Noble.
