 Complete the following phrase:  HMS Invincible was the lead ship of her class of three battlecruisers built for the Royal Navy during the first decade of the twentieth century and the first battlecruiser to be built by any country in the world. During the First World War, she participated in the Battle of Heligoland Bight in a minor role, as she was the oldest and slowest of the British battlecruisers present. During the 