Middlesex
Middlesex is one of the historic counties of England. It ceased to be an administrative county in 1965 following the passing of the London Government Act 1963. The historic county boundaries largely follow three rivers: the Thames in the south, the Lea to the east and the Colne to the west, with a line of hills forming its northern boundary with Hertfordshire. The historic county of Middlesex now lies almost entirely in the ceremonial county of Greater London, with smaller parts in the counties of Hertfordshire and Surrey. The county is the second smallest of the historic counties of England, after Rutland.
Source: Wikipedia
The aging population in Middlesex, London, is significant, with over 11 million people aged 65 and older, accounting for 18.6% of the total population. This includes more than 527,900 individuals aged 90 and over. The population is projected to continue growing, with an additional 8.6 million people aged 65 and over expected by 2050.