What is the role of "that" leading the sentence?

This is a sentence in the Queen’s speech regarding the fight against Covid-19. It starts with a "that" which I think is not necessary. As "the attributes" already serve as the subject of the sentence, then what is the role of "That"?

I hope in the years to come everyone will be able to take pride in how
they responded to this challenge. And those who come after us will say
the Britons of this generation were as strong as any. That the
attributes of self-discipline, of quiet good-humoured resolve and of
fellow-feeling still characterise this country. The pride in who we
are is not a part of our past, it defines our present and our future.