Archibald Campbell, builder of Ft. Williams, Calcutta,

 Ft. William,Kolkata.
Ft. Williams was an important trading post in Bengal(now W. Bengal) in the British Empire built in 1706 by the British East India company to carry on their mercantile trade activities including exports. The fort was heavily damaged during the skirmishes between the Nawob of Bengal and the company which purposely breached the trade contracts by not paying taxes and fortification of the trading post, etc.

Archibald Campbell.builder of Ft.William Kolkata.
A.Campbell with his 2nd wife Anna.
 In 1768, Campbell, an engineer by profession was a member of the Corps of Engineers, employed by the British East India Company in Bengal to work on Fort William that was  first built in 1706 in Calcutta. The company wanted to make the fort strong enough to withstand any future attack. The British were not on good terms  with  the Nawob of Bengal. who in 1756, attacked the fort and conquered Calcutta.It took a while for the British to recover the  areas from the Nawob.
Ft.William, Kolkata. Credit:
Though the construction of the 'new' Fort William began (soon after the battle of Plassey in 1857) in 1858 it was not completed until 1781 on account of scarcity of trained artisans, workers and an inadequate supply of construction materials. Further, people had to be trained to build according to  European style and standard  for which  bricks,etc  had to be made  suitable to the task at hand. The Company's inconsistent and uncertain changes in plans and, of course, some dishonesty on all sides did not get the project going.

Most Chief Engineers like Brohier, Martin and others were arrogant, obstinate and worst of all, niggardly and did not last for more than two years. The workers were not treated by the British sahibs with dignity and respect for their talents and skills. By the time Lieut Col. Archibald Campbell arrived to take up his position as the chief engineer of the project, the situation was chaotic. Archibald  was  energetic and methodical and was a man of high integrity and good ability. He arrived on  February 20,1769, and the building works at Fort William  were at last reduced to some order and system.When he assumed charge in Fort William, he made his assistants keep books in which they were obliged to record every important engineering transaction.

In modern India "the 'new' Fort William is still in use, and is presently the headquarters of the Eastern Command of the Indian Army. It is heavily guarded by the Indian Army and civilian entry is restricted.  (vide  wikipedia)

Campbell made a fortune in India in an honest way unlike many British officers who were corrupt.  While he was in Calcutta, Campbell laid the foundation of his  vast wealth. With Captain Henry Watson, he (privately) invested in a dockyard at Kidderpore (south of Fort William). The two men acted as contractors for building and repairing ships until the Government purchased their concern. It was a legitimate business, as private trade by Company employees was still allowed. After his return to Britain, Campbell became the Member of Parliament for Stirlin and bought Knapdale's  Inverneill Estate.The Dictionary of National Biography notes that Campbell made a fortune trading in silk.