This had been begun as the Mercer's Hall Marine Company, or Undertaking kept at the Royal Exchange for insuring ships and merchandise at sea.

Lord Onslow then sought a means of avoiding the difficulty by his company acquiring the charters of Society of Mines Royal and Company of Mineral and Battery Works, which declared itself open for assuring ships and merchandise in March 1719.

They and another insurance enterprise, the London Assurance Company, each offered £300,000 towards George I's Civil List debts.

[3] Under the terms of this legislation, the Royal Exchange and the London Assurance Company were the only incorporated bodies chartered to write marine insurance.

Although this eliminated competition from other corporations, private underwriters, such as those at Lloyd's of London would remain in business.