The FCA’s joint executive director of enforcement and market oversight told investors “there is light at the end of the tunnel.”

She said: “Investigations and operations like this take time. They involve painstakingly looking at large amounts of evidence. To support our work, we’ve issued almost 60 information requests, gathered over 46,000 items of relevant material and interviewed 18 witnesses.

“We appreciate that the time taken causes immense frustration, particularly for those with money trapped in the fund. This is a case we need to get right, and there aren’t short cuts to doing that.”

She asked investors to vote on a proposed redress scheme, which will see them get back up to 77p in the pound.

The FCA announced the scheme in April with a proposed compensation package of up to approximately £235m for investors who were trapped in the fund when it was suspended.

The money will come from Link Fund Solutions (LFS), the authorised corporate director of the fund, responsible for managing the liquidity of the fund.

She said the redress proposed reflects the FCA’s assessment that those who held investments when the fund was suspended lost out compared to those who got out early. She said: “That’s because some of the remaining investments were less liquid and took much longer to sell. Regulation cannot compensate for an investment strategy turning sour – and in this case the strategy was transparent and well disclosed. Risk of loss is the flip side of potential return. Instead, we’ve focused on the unfairness of poor liquidity leading to investors losing out.”

Link Group, the ultimate parent of LFS, has agreed to voluntarily contribute up to £60m of the £235m to bolster the redress. The money would not be available to investors through either separate legal action or any other action the FCA, or anyone else, could take, she said, adding: “This is despite unrealistic promises that that there could be more money recovered through private litigation.”

This redress scheme, together with sales from the suspended fund, means investors will potentially receive back up to 77p in the pound for their losses.

Ms Chambers told investors: “This is the quickest and best way to return as much money to investors as possible compared to other means.”

She said the decision about the redress scheme is “rightly down to Woodford investors – a majority of those who vote need to support it for it to go ahead, as well as holders of seventy-five per cent by value of relevant claims.”

She said investors should be given more information in July.

If investors vote in favour of the scheme, it won’t be the end of the story, she said: “LFS aren’t the only party under investigation. These continue and we’ll share as much as we can as soon as we can.”

Saturday 3 June was the fourth anniversary of the Woodford Equity Income Fund being suspended.