Alex appeared in Chichester Festival Theatre’s Mack & Mabel this summer and was touring with the show at the time of his death.
Chichester Festival Theatre artistic director Jonathan Church said: “We are so sad to confirm that Alex Giannini died suddenly of natural causes, shortly before the second performance of Mack & Mabel at Theatre Royal, Plymouth.
“Alex’s performance as Mr Baumann in Mack & Mabel was an absolute joy and he was a much-loved member of the company. He first worked at Chichester on The Front Page, then Oklahoma! and more recently The Resistible Rise of Arturo Ui.
“Our thoughts are with his wife and family and also the Mack & Mabel company as they continue their UK tour. He will be greatly missed by us all.”
His death meant the evening’s showing of Mack and Mabel at the Theatre Royal was cancelled about an hour before curtain-up.
Agents Felix de Wolfe added: “An incredible life force has left the building.”
The theatre wrote on Facebook: “Thank you to everyone who was affected by last night’s cancellation, for your patience and understanding.”
Alex Giannini appeared in the recently-released film Legend about twin gangsters the Krays.
Alex’s TV credits included The Musketeers, Transporter, Borgia, The Taming of the Shrew, The Russian Bride, Grafters and Prime Suspect.
His films also included London has Fallen, Elizabeth: The Golden Age and Prisoners of Honour.
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