Remember, if you haven't used our clues pages yet, check out the instructions here to learn how they work and how to best utilize them.
Hint 1
While the card says "England," I believe Jason Clark is elsewhere.
Hint 2
These are some pretty famous landmarks inside each of the letters.
Hint 3
If it helps, these are all famous landmarks in the United Kingdom.
Solution
Final Solution: The letters hold the following locations: Stonehenge, Eden Project, Angel of the North, Tower of London, Tower of London (again), Lloyds, and Eden Project again. Read as an acrostic, this spells out "Seattle."
Hint 1
There's a lot to unpack here, but first you'll want to use another part of the postcard to tell you what you're looking for at these coordinates.
Hint 2
The background on the postcard back should push you in the right direction...
Hint 3
Your numbers will help you pull information from what you found at those coordinates.
Solution
Final Solution: Each of the coordinates leads to a London underground station, and the highlighted numbers will let you index into the names of those stations, giving you the message: "The boss is called Yggdrasil."
Hint 1
That's seems like a lot of panes of glass for a standard telephone booth.
Hint 2
There seems to be an odd pattern of dark & light panes of glass.
Hint 3
There's an extra column on the right that might be throwing you off, but this is a classic cipher & language.
Solution
Final Solution: The windows are in Braille and spell out "Tim Cox"
Hint 1
First, what are these images of?
Hint 2
The ship is easy, but what's that plant on the right?
Hint 3
If you think you know what this says, but don't know what to do with it, come back to this card at a later time after you've solved some puzzles and other cards.
Solution
Final Solution: The stamps are "ship" and "mint" and when put together make "Shipment".