TORONTO -- With Prince Harry and Meghan removed from their royal duties, one historian says the Duke of Sussex is of little use to the throne while living in the U.S.

鈥淲hat use is he to the Royal Marines if he鈥檚 sitting in California with bare feet? It doesn鈥檛 work I鈥檓 afraid,鈥� Hugo Vickers, a royal historian, told CTV National News.

Vickers explained that the military role requires a certain amount of on-the-ground participation which would be difficult for Harry to fulfil in his absence.

The royal duties also require a lifetime of public service, which the Queen stated would not be possible for the Duke and Duchess to continue.

鈥淚t鈥檚 obvious for some time that it was unlikely for them to come back, with all the lucrative deals they have been striking, and doing things entirely their way and rather opposite to what the Royal Family do,鈥� said Vickers.

The news comes ahead of an interview with Oprah Winfrey scheduled to air on March 7, and days after the couple announced they are expecting a second child.

鈥淚t seems to me whatever Harry and Meghan do, it all revolves around them,鈥� said Vickers.

A spokesperson for the couple said in a statement that the Duke and Duchess of Sussex remain committed to supporting the organizations they have represented.

They also said 鈥渟ervice is universal.鈥�

鈥淲hat I detect is considerable disappointment on behalf of the Royal Family, and a certain amount of irritation of Harry and Meghan,鈥� said Vickers.

Should anything happen to the Duke and Duchess of Cambridge, there will be questions regarding whether Harry should assume his royal duties to serve as king. Vickers explained this scenario could put the royals in a difficult situation.

鈥淕od forbid that anything should happen but if he鈥檚 out in California, and by the twist of fate he ends up as king, what happens then?鈥� said Vickers.

Vickers explained that it would be in the best interest of Harry and his family to forfeit the right to monarchy, rather than having the Queen purge it from him.

鈥淲hat would be the most honorable thing for Price Harry to do is voluntary surrender his right to succession to the throne for himself and his children,鈥� he said.

Vickers says he agrees with the Queen鈥檚 decision.

鈥淭his is a tough decision she鈥檚 made and I didn鈥檛 see what else she could have done - she鈥檚 absolutely right,鈥� said Vickers.