The term British Snake, Venomous is referring to the ADDER, which is a venomous snake native to Britain and other parts of Europe. It is the only venomous snake species found in Great Britain and is the country's only native reptile. The ADDER is a small snake, usually between 20 and 40 cm in length, with a distinctive zigzag pattern on its back. It is a shy creature and will usually try to escape if disturbed.