Complex sentence: Cope himself joined the demonstrations and took a prominent role in proceedings: wearing a huge theatrical costume throughout the march, he was later featured on the BBC's Poll Tax documentary, a lone protester walking down Whitehall surrounded by seven lines of mounted police.
Split into simpler sentences: Cope himself joined the demonstrations and took a prominent role in proceedings. Wearing a huge theatrical costume throughout the march, he was later featured on the BBC's Poll Tax documentary, a lone protester walking down Whitehall surrounded by seven lines of mounted police.