I heard that a long time ago that the English (like wot I am) used to
add a little mustard to their coffee. Apparently Samuel Pepys had noted
this fact in the 1600s. However, I now live in New Zealand and have
recently heard people on TV old, but considerably younger than 400
years, talking about it as something that was done here. However details
where thin.

In the UK I could always take or leave coffee. There were very few
decent coffee shops but in NZ good coffee is as ubiquitous as rugby
shirts, plastic kiwis and lord of the rings memorabilia. So now I am
very hooked on coffee.

So my curiosity about this old habit has been peeked.... Anyone tried it?

What sort of mustard was added? How much? Is it added prior to brewing?
Did it as you might imagine turn a cup of good coffee in to a vomit
inducing draft or bring out an orgasmic flavor sensation?

Maybe in the 17th century, the coffee was so old and moldy by the time
it got to England that adding mustard was the only way to get anything
from it.