A gay man fighting to win his husband equal pension rights has taken his case to the Supreme Court and is hoping for a decision which could "dramatically change the lives of thousands of same-sex couples".
Former cavalry officer John Walker, 65, wants five high court justices to overturn a Court of Appeal ruling in 2015 which went against him.
Appeal judges had decided his claim failed because it applied to a period before gay civil partnerships were recognised by the law.
As Mr Walker arrived at the UK's highest court on Wednesday, he said: "I am feeling confident. I think common sense will prevail."
Mr Walker, who was paying into a company scheme for 20 years, has argued that his husband should have the same pension rights a wife would enjoy if he was in a heterosexual relationship.
He argues that he has been making the same contributions to the pension scheme as his heterosexual colleagues and wants to ensure that, should he die first, his husband, 52, will be adequately provided for.
Mr Walker and his husband have been together since 1993 and entered into a civil partnership in January 2006, which was later converted into a marriage.
Human rights organisation Liberty, which is representing Mr Walker, points out that Mr Walker's husband would receive a pension of only a few hundred pounds a year - but if he was married to a woman she would be entitled to receive around £45,000 a year for life.
Liberty said the case "challenges an exemption in the Equality Act that lets employers exclude same-sex partners from spousal benefits paid into a pension fund before December 2005, when civil partnerships became legal".
It will be argued that the exemption is "discriminatory".
Liberty lawyer Emma Norton said "many, many others will be suffering the same injustice" as Mr Walker.
She added: "We hope the Supreme Court will drive the law into the 21st century and take a huge step towards equal pension rights for same-sex spouses and civil partners."