Lady Mary's father pressured her to marry Clotworthy Skeffington, the heir to the Irish Viscount Massereene. Skeffington's marriage contract included "an allowance of £500 a year as ‘pin-money,’ and £1,200 a year if he died." However, she rejected him. Thus, to avoid marriage to Skeffington, she eloped with Montagu. In a letter to Wortley, she wrote, "He father will have a thousand plausible reasons for being irreconcilable, and ‘tis very probable the world will be on his side…I shall come to you with only a night-gown and petticoat, and that is all you will get with me. I told a lady of my friends what I intended to do. You will think her a very good friend when I tell you she has proffered to lend us her house if we would come there the first night…If you determine to go to that lady’s house, you had better come with a coach and six at seven o’clock to-morrow." The marriage license is dated 17 August 1712, and the marriage probably took place on 23 August 1712 and the marriage occurred at Salisbury on 15 October 1712.