Commercial Union plc was a large insurance business based in London.

Commercial Union was established following a conflagration near London Bridge in 1861, known as the Great Tooley Street Fire, which destroyed a number of warehouses and wharves along the River Thames as a result of which the fire insurance companies were hit by a series of massive claims.

Consequently, they increased their fire insurance rates so dramatically that a group of local merchants and brokers decided to form their own company.

[2] It purchased the Hand in Hand Fire & Life Insurance Society, the world's oldest fire insurance company, in 1905[3] and The Ocean Accident and Guarantee Corporation in 1910 and it continued to grow by further acquisitions.

[4] Then, after completing the acquisition of North British and Mercantile Insurance, which had significant operations in the United States, in 1959, Commercial Union moved to larger and more modern facilities at St. Helen's in London in 1969.