Complex sentence: He gave the City five banks and was architect to the Bank of England from 1855 to His best known work was the Great Hall of London's Euston station (opened on 27 May 1849).
Split into simpler sentences: He gave the City five banks and was employed as architect to the Bank of England. Hardwick was architect to the Bank of England from 1855 to His best known work was the Great Hall of London's Euston station (opened on 27 May 1849).