Hi gogilvie,

It appears the the Northern Insurance Company was established in Aberdeen in 1836 as the North of Scotland Fire and Life Assurance Company.
It was incorporated under the Joint Stock Companies Registration Act and renamed the Northern Assurance Company under an act of parliament dated June 30 1848.

In January 1837, a new prospectus stated that
... "the company insures houses, manufactories, furniture, goods, and merchandise, farming stock, shipping in Port and Dock, and while Building, Repairing, or used on Navigable Canals, and all other Property, from Loss or Damage by fire".
The business also included "endowments of children, the purchase and sale of annuities, insurances on joint lives and survivorships, and every Transaction dependent on the Contingency of Life".

The great fire of Yokohama, Japan, in 1866 cost the company ?50,000 in claims, wiping out all but ?5,000 of the previous 30 years' profit.

The San Francisco earthquake in 1906 cost the company $2,420,000, which included the payment of the largest single loss paid by any insurance company in the wake of the disaster.

- It's overseas agencies were:
Lubeck, Germany (1851) also in Bremen, Hesse and Darmstadt, Bavaria, Wurtemburg, Wiesbaden, Hanover, Darbistadt (Darmstadt), Stuttgardt, Munich, Nurnberg (Nuremberg), Bamberg, Leipzig, Dresden, Oldenburg, Augsberg (Augsburg), Frankforten Maine (Frankfurt-am-Main) in 1851
Cassel, France (1851)
Basel, Switzerland (1851)
St Gallen and Schwsin (Schwyz) Copenhagen,
Denmark (1852)
Christiana (Oslo), Norway (1852)
Gothenburg (Goteborg), Sweden (1852)
Bautzen, Germany (1852)
Gera, Germany (1852)
Horsens and Schleswig, Denmark (1852) Haderisleven (Haderslev), Denmark (1852)
Altona (Altenau), Germany (1852)
Zurich, Switzerland (1853)
Vienna, Austria (1853)
Helsingfors (Helsinki), Finland (1853)
Rio De Janeiro, Brazil (1853)
Melbourne, Australia (1853)
Strasbourg, France (1853)
Paris, France (1853)
Novikoping (Norrk?ping), Sweden (1853)
Antwerp, Belgium (1853)
Malmoe, Sweden (1853)
Cassel (Kassel), Germany (1853)
Otago, New Zealand (1853)
Elberfeld, Germany (1853)
Carlscrona, Sweden (1853)
Sydney, Australia (1853)
Antigua (1853)
St Vincent (1853)
Caracas, Venezuela (1853)
Port of Spain, Trinidad (1853)
Stockholm, Sweden (1853)
Tromsoe (Tromso) and Bergen, Norway (1853) Rostock and Schwerin, Germany (1853)
Le Havre, France (1853)
Gefle (Gavle), Sweden (1853)
Drontheim (Trondheim), Norway (1854) Christiansand, Norway (1854)
Amsterdam, Netherlands (1854)
Auckland, New Zealand (1854))
Mannheim, Germany (1854)
Florence, Italy (1854)
Adelaide, Australia (1854)
San Francisco, USA (1854)
St Thomas (1854)
Geneva, Switzerland (1854)
Puerto Rico (1854)
Danzic (Danzig), Poland (1854)
Port au Prince, Haiti (pre 1854)
St Helena (1855)
Colombo, Ceylon (Sri Lanka) (1855)
Kingston, Jamaica (1855)
Calcutta, India (1855)
Demerara, Guyana (1855)
Madras, India (1855)
Singapore (1855)
Kandy, Ceylon (Sri Lanka) (1855)
Bucharest, Romania (1855)
Bahia, Brazil (1855)
Pernabumco, Brazil (1855)
Para, Brazil (1855)
Havana, Cuba (1855)
Barbados (1855)
Bombay, (Mumbai), India (1855)
Batavia, (Jakarta) Indonesia (1855)
Shanghai and Canton, China (1855)
Hong Kong (1855)
Manila, Philippines (1855)
Alexandria, Egypt (1855)
Honolulu (1855) Mexico (1855)
Wellington, New Zealand (1856)
Canada (1856)
Guadeloupe, West Indies (1856)
Martinique, West Indies (1856)
Buenos Aires, Argentina (1856)
Lisbon, Portugal (1856)
Oporto, Portugal (1856)
St Petersburg, Russia (1856)
Lima, Peru (1857)
Tacna, Peru (1857)
Valparaiso, Chile (1857)
Hobart, Tasmania (1857)
Surabaya (Surabaja), Indonesia (1857)
Java (Jawa), Indonesia (1857)
Montevideo, Uruguay (1857)
Rosario, Uruguay (1857)
Santa Fe, Colombia (1857)
St Johns, Newfoundland, Canada (1857)
Cape of Good Hope, South Africa (1858)
Bordeaux, France (1858)
Kurachee (Karachi), Pakistan, (pre-1859) Moulmein, Myanmar (Burma) (1859)
Riga, Russia (1860)
Grenada (1860)
St Lucia (1860)
St Kitts (1860)
Nevis (1860)
Warsaw, Poland (1860)
Rangoon, Myanmar (1860)
Victoria, British Columbia, Canada (1860)
St Louis, United States (1861)
Antwerp, Belgium (1862)
Berlin, Germany (1862)
Tettuang via Wurttemberg, Germany (1862)
Porto Rico, Africa (1862)
Porto Planta (1862)
Hamburg, Germany (1862)
Guayaquil, Ecuador (1862)
Bangkok, Siam (Thailand) (1863)
Mauritius (1863)
Nassau, Bahamas (1863)
Brussels, Belgium (1863)
Penang (Pinang), Malaysia (1863)
Canary Islands (1863)
Tientsin (Tianjin), China (1863)
Yokahoma, Japan (1863)
Berbice, Guyana (1863)
Xiamen and Amoy, China (1864)
Constantinople (Istanbul), Turkey (1864)
Caera, Brazil (1865)
Cadiz, Spain (1865)
Malta (1865)
Galatz, (Galati), Ibraila (Braila) and Wallachia (Valahia), Romania (1865)
Moldova (1865)
Beyrout (Beirut), Lebanon (1865)
Smyrna, Turkey (1865)
Nova Scotia, Halifax, Canada (1866)
Port Louis (1866)
Guernsey, Channel Islands (1866)
New Brunswick, Canada (1866)
Montreal, Canada (1867)
Monserrat (1867)
Prussia (1867)
Porto Alegre, Brazil (1868)
Maranham, Brazil (1868)
Parahiba (Paraiba), Brazil (1868)
Dublin, Ireland (1868)
La Guajara, Brazil (1868)
Londonderry, Ireland (1868)
Nicosia, Cyprus (by 1885)
Formosa (Taiwan) (by 1907)

Read more at their link above

Will see what I can find on the Imperial Insurance Company and post later

Thanks very much. I have sent off an enquiry to the archivist of Aviva Insurance, the current reincarnation of Northern Insurance as per the URL you sent.
It is only an outside chance they will have anything but I await the reply with great interest.
gogilvie