BlackRock purchased the shares on 23 May, according to a regulatory filing, meaning it paid in the region of 282p to 291p per share.
The firm had backed the Jupiter IPO last summer with an initial purchase of 23.5m shares, which gave it a 5.1% stake in the company. The 23 May transaction saw it increase its share holding to 9.93%.
Blackrock also holds more than 473,000 contracts for difference in Jupiter, giving it an additional 0.10% of voting rights and bringing its total stake in the firm to 10.03%. That stake is now worth over £130m at current market prices.
