Those Warm English Beers

I posed the following question to my British friend, Nick Morely:

What is the name of those warm English beers that you get in pubs in England? Hand pull? Hand pour?

And Nick replied with this thoughtful and thorough answer:

You are referring to a cask ale. These are typically beers that are kept at room temperature or very slightly chilled in casks.

Unlike the beer which appears from one your taps, those traditional British ales have no gas added between the time the ale leaves the cask and whence it appears from the tap. Therefore the bar maid has to pull down the pump to generate pressure to draw up the beer and into the glass or you would simply draw it straight off the cask via a tap. They probably represent less than 10% of the beers that get sold in UK, as most people drink lagers or ales which have gas added between cask and tap.

You would order these beers by name by seeing what was on offer rather than saying give me a “hand pull”. Honestly, if you asked someone in my local for a hand pull you would get your nose broken.

Anytime you can use "whence" in a sentence is alright by me.