I was looking around the National Archives website and discovered that due to the restricted access because of COVID-19, they are allowing free downloads of much of their archive. You just need to register and verify your email address, then you can add 10 items at a time and checkout for free, up to 50 items per 30 days, after checkout you get download links for the pdf’s. WW1 tank diaries start at WO 95/1-1.
