A senior investment banker, who conspired with him, was given four and a half years imprisonment.

The case was brought by the Financial Conduct Authority and involved a three-month trial at Southwark Crown Court. It related to events between November 2006 and March 2010.

Chartered Accountant Andrew Hind and investment banker Martyn Dodgson were found guilty of insider dealing on a number of shares including Legal & General, Just Retirement and Paragon Group.

Confiscation proceedings will also be pursued against both defendants.

In sentencing Mr Dodgson and Mr Hind, the trial judge, His Honour Judge Pegden, remarked that their offending was “persistent, prolonged, deliberate, dishonest behaviour.”

Mark Steward, FCA director of enforcement and market oversight, said: “This case involved serious offending over a number of years, conducted in a sophisticated way using deliberate techniques to avoid detection. Dodgson was an approved person who was entrusted by his employer with sensitive and valuable information. He betrayed that trust by exploiting the information for his own benefit, conspiring with Hind to deceive the market

”Insider dealing is ever more detectable and provable. And this case shows lengthy terms of imprisonment, not profits are the real result.”

This investigation was conducted in partnership with the National Crime Agency.

Oliver Higgins, National Crime Agency Branch Commander, said: “Dodgson and Hind tried to prevent us from uncovering their insider dealing by using unregistered mobile phones, encoded and encrypted records, and transferring benefit using cash and payments in kind.

“The NCA were able to support the FCA by carrying out surveillance and providing niche capabilities, including the deployment and monitoring of a listening device that recorded key conversations.”

Mr Dodgson was employed by Morgan Stanley, Lehman Brothers and Deutsche Bank. He worked at Morgan Stanley as a vice president in Global Capital Markets until January 2007, and then at Lehman Brothers as an executive director in the European Investment Banking Division from July 2007 to September 2008.

He moved to Deutsche Bank in October 2008 as a director in the Corporate Broking Department and was later promoted to managing director. He was Financial Services Authority approved throughout the period.

Mr Hind, a businessman, is a property developer and a qualified Chartered Accountant.

The FCA said: "Mr Dodgson and Mr Hind, who were close personal friends, instigated this insider dealing conspiracy. They agreed to deal secretly, sometimes on the basis of inside information. Mr Dodgson sourced inside information from within the investment banks at which he worked, either through working on transactions himself or through being able to glean what his colleagues were working on."

The two were convicted as part of the Operation Tabernula investigation - which the FCA says has been its largest and most complex insider dealing investigation.

The two convictions – alongside those of Paul Milsom, Graeme Shelley and Julian Rifat – brings to five the number of convictions secured in the Operation Tabernula insider dealing investigation.

• Three other defendants, Andrew Grant Harrison, Ben Anderson and Iraj Parvizi, were acquitted.