To find this cache you first need to complete the Adventure Lab of the same name – that will take you to look at several different styles of building around Sherwood. You will visit a mansion and a distinctive house designed by a renowned architect, but you will also see a cluster of almshouses, a tram depot and an early cinema.
Each stage of the Adventure Lab will give you some information relevant to his cache, and you should now be in possession of letter/number combinations. All you need to do now is to convert the letters into numbers and head to the calculated coordinates to find the cache.
The cache can be found at: N52 5A.BCD W001 0E.FGH