The line has signed a memorandum of understanding with German shipbuilders Meyer Werft for two new vessels in its Evolution-class, the first of which is expected to be delivered in 2022.

Silversea has also signed a contract with Dutch shipbuilder Shipyard De Hoop to construct a new expedition vessel, Silver Origin, to serve the Galapagos Islands itinerary currently sailed by Silver Galapagos.

Silver Origin is expected for delivery in March 2020.

The agreements are expected to be completed in the first quarter of 2019.

Silversea’s expansion follows Royal Caribbean Cruises Ltd (RCCL) taking a controlling stake in the brand earlier this year.

Manfredi Lefebvre d’Ovidio, Silversea executive chairman, said: "We are delighted to have entered into an agreement with Meyer Werft on the Silver Evolution series and De Hoop for Silver Origin.

"With our guests in mind, we are pushing the boundaries of ultra-luxury cruising, as well as expedition cruising in the Galapagos Islands and beyond, redefining the concept of immersive travel."

Richard Fain, chairman and chief executive of RCCL, added: “"We are excited to get to work helping Silversea grow and realize its ambitions.

"There is tremendous potential in the ultra-luxury and expedition markets of the cruise industry, and we believe discerning travellers will embrace the exciting designs Silversea is imagining for them."