While the Mk V was a success, the Germans soon learned a lesson and simply made their trenches wider. This meant that the Mk V simply fell in and couldn't get across. The original attempt at this was to extend the tracks out backwards, giving it an odd fishtail like appearance. Major Philip Johnson saw these designs and worked out that it was much more efficient to simply extend the tank. This provided more crew space and some additional gun placements. This became the Mk V*.
Unfortunately by simply extending the chassis, they had also increased the turning radius and caused a lot of strain on the tracks, causing lots of thrown links. The curve of the tracks was improved and more powerful engine was fitted. This became the Mk V**