He said that William and others in the Royal Family “are saying he has gone a step too far” in airing private details in public.
The royal expert added: “But, when he comes over in July, there will be a chance for them to just sit around the table and solve it and tell him to shut up.”
Both Prince Harry and Prince William are expected to attend the unveiling ceremony on what would have been Princess Diana’s 60th birthday.
However, questions have arisen surrounding the Duke of Sussex following his recent comments about the Royal Family.
There has been speculation that Harry may not return for the event due to tensions between the brothers.
However, Mr Bell suggested that Harry would in fact attend the event.
He also downplayed suggestions that the Queen would strip Harry of his royal titles, amid renewed calls for such action.
As many as 25,000 people have signed the petition started by royal expert Lady Colin Campbell.
The petition claims Harry does not need his royal titles and has invited him to “voluntarily” ask the Queen to put his “royal style, titles and rank into abeyance”.
Ms Campbell told The Daily Star: “I started the petition because I think it’s the right thing to do.”
She insists that the Duke of Sussex “doesn’t need” the royal titles as “he is too big for them now” as he “still gets publicity and attention”.