Documentary in which Anne Robinson asks what the secret is to a happy relationship. Journeying around the UK, Anne meets couples from very different backgrounds, all of whom think they have the answer. Entering the couples' homes, Anne finds out their different relationship secrets. How have middle-aged Janet and Malcolm survived an affair? What happens if you don't want to just sleep with your spouse? To answer this, Anne meets a polyamorous group in Leeds. She also finds out whether marrying the lord of the manor is all it is cracked up to be and whether agreeing to an arranged marriage can hold the key to long-term happiness. Anne also gets two couples to delve into each other's relationships to see what they can learn. Whitney and Megan are soulmates who can't bear to be apart - they even go to the loo together. David and Claire don't even live together and believe it keeps their marriage fresh. What will they make of each other's relationships?