The open letter calling for his release featured film A-listers Josh O’Connor, Benedict Cumberbatch and Javier Bardem, as well as musicians Fontaines D.C. and Sting.
At issue is the near-ubiquitous practice of brands subcontracting work to suppliers, who in turn contract to others, amid ever-tighter margins and scant oversight of labour conditions.
In his book, the 87-year-old former monarch reflects on well-known moments from Spain's history as well as his extramarital affairs and financial scandals.