Murder at Down Street Station is the second in Jim Eldridge’s London Underground series. It’s $0.99 right now at Kindle US, but sadly not matched (at least as of now) at Kobo US.
Kindle US:
https://www.amazon.com/dp/B0BFCD3MSB
Kobo US (for price check/match):
https://www.kobo.com/us/en/ebook/mur...reet-station-1