Quiet Nights is different enough that I don't find it to be a close match to Nightcap; however, there does seem to be a Dunhill connection with a number of Pease blends. For the Old London series he has written that his original idea was to create a series of blends that were connected to time of day:
"I’d originally had it in mind to create blends that seemed appropriate for different times of day. Chelsea Morning, for enjoyment with the morning coffee, Afternoon Tea for later in the day, Cocktail Hour for a nice interlude before dining, and Quiet Nights for the relaxation of the evening, the final puffs before retiring. Sounds good. But, it’s turning out not to be so easy."
It's clearly a Dunhill-like concept, (i.e. Early Morning Pipe, Mixture 965, Apertif, and Nightcap).