Answer:

zed

Answer	Crossword Clue
ZED	British ending
ZED	End of the British alphabet
ZED	Queen Elizabeth spells her name with one

ZED	End of a line on the Underground?
ZED	The end of the British monarchy?
ZED	Series ender in London
ZED	End of the Oxford English Dictionary
ZED	What an English organization lacks?
ZED	See 44-Across
ZED	One of two parts of a British puzzle?
ZED	Part of Queen Elizabeth's makeup?

ZED	Lack of authorisation?
ZED	Final section of the 40-Across
ZED	End of a line in England
ZED	Letter in 145-Across
ZED	Letter in the Globe and Mail
ZED	Part of an English wizard's spell?
ZED	London Zoo opening?
ZED	Lack of organisation?

ZED	Something Elizabeth II has?
ZED	Letter from London
ZED	Overseas finale
ZED	Finish overseas
ZED	Letter in the Daily Mirror
ZED	Last letter in Leeds
ZED	BBC finale?
ZED	Brit's finale

ZED	O.E.D. ender
ZED	London Zoo feature?
ZED	From A to ...
ZED	Last letter in London
ZED	End of the English alphabet
ZED	End of the Tudor line?
ZED	British finale
ZED	End of the British Empire?

ZED	British alphabet ender