The Express - Couples warned 'devil is in the details as inheritance tax myth may cause huge bill 

“Michael Culver, chairman at Solicitors for the Elderly (SFE) said: “A common myth is if couples are in a relationship for decades they may benefit from the same exemptions as those who are spouses - which is not true…”

https://www.express.co.uk/finance/personalfinance/1785835/inheritance-tax-myth-unmarried-couple