An A Tritton is listed as having been granted a US patent in 1919. Closer examination shows this to have been a W A Tritton of Lincoln and the patent was file in 1917! The patent was for an endless track system
The detailed track link and road wheel drawings on pages 2 and 3 are identical to those in his British patent (127,855; application date 1 Dec 1916, granted 19 June 1919), but the sketched vehicle layout on page 1 is completely different. His US patent shows a Holt tractor type layout, whereas his British patent shows a Little Willie type track frame. Very odd.
Partly, I suspect. I've downloaded a hell of a lot of patents from the EU website, and most took anything from a few months to five years between application and being granted. Pre-war patents generally took a few months to a year, but after 1914, you're looking at years. Yes, secrecy probably played a part (it's striking that so many patents appied for in, say, 1915 or 1916 didn't actually get granted until 1919 or so). Two years is not at all unusual. On the other hand, there are some patents applied for after the war which took years to grant (for example, one of Wickersham's many patents was applied for in 1919 and not granted until 1924!).