A selection of Victorian love letters written by the parents of a former prime minister are being published online for Valentine’s Day.

The letters were written in 1843 by James Maitland Balfour, then MP for Haddington, and his bride-to-be, Lady Blanche Cecil, the daughter of prominent nobleman, the Marquess of Salisbury.

Their eldest son, Arthur, would go on to be prime minister.

The letters were among a number of papers bought for the national archives last year by National Records Scotland (NRS).

Archivist Veronica Schreuder said: “History already documents the union of these two immensely influential families but these private letters show us the tender young couple in love, eager that they would get on with each other’s families. We’re putting extracts online today so people can read them for themselves.”

The letter was dated July 15 1843 – a month before the couple’s wedding.

Mr Balfour proposed and she accepted, which triggered a flurry of excited letters between family members. There are congratulations from his parents, his brother-in-law and even her nine-year-old brother.

Mr Balfour wrote: “My dearest Lady Blanche, I cannot leave town with no chance of seeing you again for many months without doing that which must either make me the happiest or most wretched of men.

“O Lady Blanche, I love you deeply fervently and O how happy should I be if I could only hope that that love was returned.”

Ms Schreuder added: “In some ways their story is a sad one as James Balfour died only 13 years later at the age of 36 from TB (tuberculosis) but it was also a successful marriage.

“They had eight children: three daughters and five sons, who would all go on to lead influential lives. Their eldest son, Arthur, followed in the footsteps of his uncle to become prime minister in 1902.”

The couple were marred at Lady Blanche’s family home, Hatfield House, in Hertfordshire, at ages 23 and 18.

The Duke of Wellington, then leader of the House of Lords, was among the guests and he gave them the use of a property on his estate for their honeymoon.

The couple went on to have a family home at Whittinghame, East Lothian, and an estate at Strathconon in the Highlands.