From the Tank Museum:

In the 25th Tank Chat David Fletcher explores the First World War Mark VIII tank. The Mark VIII tank, also known as The International was a joint project between the British and American forces, following their entry into the war. Once the designs had been refined massive orders were placed in 1918 and then swiftly cancelled with the end of the war. In the end six Mark VIII tanks were built for Britain of which The Tank Museum’s is the sole surviving example.