Most chief executives of Aim companies will argue that their shares are undervalued, while investors will complain that small company stocks are illiquid. Both sides have a point, but the situation is even worse for the US companies that join the junior market.

They have usually come to Aim to avoid the burden of Sarbanes-Oxley - but the land of the free has a long regulatory reach. It has been felt by Protonex, a US fuel cell company that floated on Aim in June last year. Whole weeks, if not months, have passed without a single share trading.