The 141-year-old building is where engineer Guglielmo Marconi established the world's first wireless communications.
It was rebuilt in 1926 and hailed as a seaside architectural triumph.
The Haven Hotel housed Belgian refugees during the First World War and became a military contact point during the Second World War.
It was purchased by FJB Hotels in 1976 and has since hosted a range of notable guests.
These include poet Robert Browning, John Major and the Real Madrid football team, featuring the likes of Cristiano Ronaldo, Kaka and Karim Benzema when Los Blancos played AFC Bournemouth in a friendly in 2014.
In 2017, businessman Richard Carr revealed his vision to refurbish The Haven and The Sandbanks Hotel.