Investigators from the Financial Services Authority, probing the split capital trust scandal, are focusing their attention on a series of rescue rights issues launched in 2001 and early 2002.
Critics of the fundraisings believe the prices of the split capital trusts may have been artificially inflated at the time of the rights issues, contributing to the trusts' rapid collapse a few months later.
So far more than 20 split capital trusts have either been forced into receivership or had their shares suspended in a scandal that has cost tens of thousands of people their savings.
Attempts to bring to account the managers from the companies that ran the trusts - such as Aberdeen Asset Management, BFS and Exeter - have so far been unsuccessful. Two law firms have attempted to put together legal actions, but neither has issued a writ.
A parliamentary inquiry embarrassed major figures in the scandal but brought no concrete action. And an investigation by the Financial Services Authority has yet to produce any sanctions.
The major stumbling block is that investment trusts are public companies, and so are not investment products under the law. This limits the FSA's scope for action.
Sources close to the investigation have told The Independent on Sunday that the FSA is now concentrating on the desperate attempts to rescue the split capital trusts as the value of their assets started falling during 2001 and 2002.
As many of the trusts held shares in other trusts, the fall in the value of one triggered a chain reaction. Falling asset values made banks that had lent to the trusts worried about their loans.
To try to shore themselves up, some of the trusts launched rights issues.
Though it appeared that the trusts were raising cash, what happened was that other trusts, which were their shareholders, merely gave them "assets" in exchange for shares in the trust making the rights issue. These assets were often shares in other trusts, and many of those trusts were in as much trouble as the ones making the rights issue.
The FSA is probing whether these deals artificially inflated the value of the shares being transferred, creating a false market. When the value of the transferred shares then fell, the trusts that had "acquired" them quickly ran into trouble.
Among the rights issues under investigation are a £62m issue by Aberdeen Preferred Income Trust in January 2002, £46m raised by Aberdeen Media & Income in April 2001, and £42m raised by Dartmoor Trust in September 2001. The two Aberdeen trusts are now in receivership and shares in Dartmoor are suspended.
Aberdeen, the largest manager of split capital trusts, denied there was anything out of the ordinary in the practice of share swapping.