Actor Corin Redgrave (search), the brother of actresses Vanessa and Lynn Redgrave, was in critical condition Friday after suffering a heart attack, the hospital treating him said.

Redgrave, 65, had a heart attack Wednesday at a meeting on the rights of travelers, or people who move from town to town in Britain and live in encampments.

His screen credits include 2004's "Enduring Love (search)" and 1994's "Four Weddings and a Funeral (search)."

In addition to his acting career, he is also a political activist who has been outspoken against the detention of terrorist suspects without charge in Britain and at the U.S. naval base at Guantanamo Bay, Cuba.

Basildon Hospital in Essex, outside London, said Redgrave had improved slightly from Thursday night to Friday morning but remained in intensive care.

"The Redgrave family would like to thank the media for respecting their privacy at this extremely difficult time," the hospital said in a statement.

Corin and Vanessa Redgrave last year founded a political party called Peace and Progress to advocate for human rights.