The Internet Archive operates under "controlled digital lending" and fair use for abandoned media. ITV has not officially released Season 4 since 1986. No one is losing money because no one is selling it. However, if you live in the UK, use a VPN if you are concerned about copyright trolls—though historically, the rightsholders have ignored this revival for three decades.
: Enthusiasts occasionally upload VHS-to-digital transfers. Some community members have claimed to possess up to 11 of the 13 episodes, though a complete, high-quality set remains rare. mind your language season 4 internet archive new