Saba Capital Management is appealing to the shareholders of seven U.K. investment trusts in an effort to take control of the closed-end funds and boost their returns.

Saba, which was founded by the activist investor Boaz Weinstein, has issued a letter that calls on shareholders to replace the boards of directors of Baillie Gifford U.S. Growth, CQS Natural Resources Growth & Income, Edinburgh Worldwide Investment, European Smaller Companies, Henderson Opportunities, Herald Investment and Keystone Positive Change.

The New York-based hedge fund has requested general meetings at the funds because the “current boards have failed to hold the investment managers accountable for the trusts’ wide trading discounts to net asset value.”

Saba’s total investment in the trusts is said to be worth £1.5 billion ($1.9 billion). The hedge fund is the largest investor in each trust, with stakes ranging from19% to 29%.

“What caught my attention for the past three years is that the U.K. trust industry’s discounts have deepened as a consequence of investors losing faith in managers after shockingly poor performance in certain trusts,” the hedge fund said in its letter.

Saba is proposing that two of its staff become directors of each trust, and the reconstituted boards can then select the hedge fund to become the trusts’ new manager. Saba said it would shift the trusts’ mandates to instead focus on buying other discounted trusts.

Saba’s letter said the firm “prefers private engagement with the boards of the trusts we invest in, but underperformance, persistent trading discounts and disengaged management teams leave us no choice but to act.”

The hedge fund said it had requested each of the trusts’ boards to hold their meetings as soon as possible, by early February at the latest.

Saba has been waging activist campaigns in the U.S., where the firm invests in closed-end funds trading at steep discounts and then pressures the funds’ managers to close the gap.

The hedge fund manages $5.5 billion in assets from its offices in New York and London. It was founded by Weinstein in 2009, as a lift-out of the Deutsche Bank proprietary credit trading group he started in 1998.

Weinsten is perhaps best known for his winning bet against the JPMorgan Chase trader known as the “London Whale,” who ended up costing the investment bank more than $6 billion in 2012.