Churchill's preferred whisky and the limits of a single favourite

What was Churchill's preferred brand of Scotch?

The answer does not settle on one favourite; it names Johnnie Walker Red Label and Black Label among several drinks.

A single preferred brand is treated as debatable. Johnnie Walker Red Label and Black Label are both named among the whiskies Churchill enjoyed. The answer also describes a small amount of whisky diluted in a large glass of water or soda. Pol Roger is initially misidentified and then corrected to champagne. The correction matters when following the list, which includes different types of drink.