What's the secret to a happy marriage? You've probably heard a lot of answers to that over the years, but this one-off documentary will try to find the solution in a London borough called Brent. Why there? This area boasts one of the highest marriage rates and lowest number of divorces in the UK. We'll meet five of Brent's married couples ranging from seven to 47 years of marriage. They discuss everything from the importance of sex in a relationship, the ups and downs of having children and whether they have ever been tempted to stray.