Aurea Concesiones de Infraestructuras, the Spanish motorway operator, has taken the unusual step of not revealing advisers for its €2.4bn ($2.1bn) merger with rival Iberica de Autopistas (Iberpistas).

The two companies are close to completing the deal, and Santander Central Hispano is thought to be advising the shareholders of Iberpistas, but Aurea's shareholders do not appear to have financial advisers.