Observer staff were told that the investment would “help to safeguard its future” as a standalone product.
Founded in 1791, the Observer is the world’s oldest Sunday newspaper.
Mr Harding, editor of Tortoise, said: “We believe passionately in its future – both in print and digital.”
He added: “George Orwell described the Observer as ‘the enemy of nonsense’. We’re excited to show readers, old and new, that it still is.”
