Duke Henry, actually Duke Henry of Mecklenburg-Schwerin (Heinrich Wladimir Albrecht Ernst; or in Dutch, Hendrik Wladimir Albrecht Ernst; 19 April 1876 – 3 July 1934) was prince consort of the Netherlands as the husband of Queen Wilhelmina of the Netherlands. He was the longest-serving consort of the Netherlands.
The marriage was an unhappy one, and produced only one child, Juliana.
Prince Henry was known to have had numerous extra-marital affairs, at least one of which resulted in illegitimate offspring; during her widowhood, Queen Wilhelmina paid monthly allowances to three known ex-mistresses.
Mein Abbo-Wenneker (later Lier-Wenneker, 1887-1973), gave birth to a total of six children; the older two, sisters Christina Margaretha Abbo & Edith Abbo (later Sheep-Abbo) were ostensibly the daughters of Mein’s first husband, Dhr. Abbo, but strongly rumored to have been fathered by Prince Henry. By then a widow, Mein in 1918 gave birth to Prince Henry’s acknowledged son, Albrecht Willem (known as Pim Lier) (22 Jul 1918 – 9 Apr 2015).
It is rumoured that, overall, Prince Henry fathered between three and ten illegitimate children, but firm proof remains elusive.
As for the cache, it's a park (right under GZ) and grab with no complications.