In his article 'The benefits of a liquid market' (11 October, 2007), Tim Stocks describes convincingly the damage to the liquidity of US stocks trading on the Alternative Investment Market (AIM) caused by the old-fashioned, paper-based settlement system widely used to comply with Securities and Exchange Commission (SEC) Regulation S.

There is a solution to this problem, to which Stocks alludes in passing. SIS SegaInterSettle, the Swiss clearing and settlement agency, currently offers in the London market a system that combines the benefits of dematerialised settlement with the capability to comply strictly with Regulation S. This system has proved itself capable of increasing significantly the liquidity of US securities.

In fact, the SIS system has been improved in three important ways since it was announced in 2006. First, a critical part of the system, which had required human intervention, is now fully automatic. Second, the system has been modified to permit US 'qualified institutional buyers' to purchase Regulation S stock under Rule 144A. Finally, UK brokers are no longer required to perform the intermediary role of 'lead manager and main paying agent' because the registrars now communicate directly with SIS.