Complex sentence: GHQ Liaison Regiment (known as "Phantom") was a special reconnaissance unit first formed in 1939 during the early stages of World War II and based at Pembroke Lodge, a Georgian house in Richmond Park, London.
Split into simpler sentences: GHQ Liaison Regiment (known as "Phantom") was a special reconnaissance unit first formed in 1939 during the early stages of World War II. Its Regimental headquarters was Pembroke Lodge, a Georgian house in Richmond Park, London.