Investing.com -- Standard Investments has cut its stake in Johnson Matthey (LON: JMAT ) by half, scaling back after a six-month activist campaign that led to sweeping changes at the British specialty chemicals group.

Regulatory filings show that Standard now holds a 4.75% stake, down from the previously reported 9.52%. The firm appears to have taken advantage of the recent share price recovery, which saw Johnson Matthey stock climb more than 35% from December lows to above £18 ($24.50).

The activist’s remaining stake includes a 1.77% direct holding and close to 3% via cash-settled equity swaps, according to the filing.

Standard Investments, part of New York-based Standard Industries, had launched its campaign in December 2024, when it held an 11% stake, then the company’s largest.

In an open letter, co-CEOs David Winter and David Millstone criticized Johnson Matthey’s leadership for “sustained underperformance” and noted shareholders had lost 53% during the chairman’s six-year term.

The pressure campaign triggered a series of changes. In January, the company moved to address two key activist demands, announcing a new board investment committee to focus on “investment strategies and capital allocation” and halting investment in its Hydrogen Technologies unit.

A broader board shake-up followed in February, including the planned departure of chair Patrick Thomas, who had been singled out by Standard.

Momentum continued in May, when Johnson Matthey said it would sell its catalyst technologies unit to Honeywell (NASDAQ: HON ) for £1.8 billion. The group said the sale would result in a “highly streamlined group,” with £1.4 billion of the proceeds earmarked for shareholder returns.

The market reacted positively, sending shares up 30% on the day. Analysts called the agreement a “surprise value unlock.”