Short answers, pulled from the story.
Hertfordshire sits immediately north of London, forming a ceremonial county in the East of England. Its borders were roughly fixed by the Counties (Detached Parts) Act 1844 which eliminated exclaves.
The boundary was amended when, in 1965 under the London Government Act 1963, East Barnet Urban District and Barnet Urban District were abolished. Their area was transferred to form part of the present-day London Borough of Barnet while the Potters Bar Urban District of Middlesex was transferred to Hertfordshire during this same period.
The highest point in the county is at 247 meters AOD on the Ridgeway long distance national path. This peak lies on the border of Hastoe near Tring with Drayton Beauchamp, Buckinghamshire.
Saint Alban remains the Patron Saint of Hertfordshire today after his martyrdom took place at Verulamium in 57 AD. He was beheaded on Holywell Hill where his yellow saltire on a blue field is reflected in the flag and coat of arms of Hertfordshire as the yellow field to the stag or Hart representing the county.
Letchworth became the world's first garden city in 1903 while Stevenage became the first town to redevelop under the New Towns Act 1946 which carried the reference number 9 & 10 Geo. 6. c. 68.