A letter from Robert Burns describing a lads' night out is going on display for the first time in more than 100 years.

It was sent in August 1786 after the poet spent a rowdy evening in Maybole, Ayrshire, with school friend William Niven.

The letter was bought at auction last year by the National Library of Scotland and will go on display on Thursday to celebrate Burns Night.

Burns wrote: "I thank you with the most heartfelt sincerity for the worthy knot of lads you introduced me to.

"Never did I meet with so many congenial souls together.

"To each and all of them make my most friendly compliments particularly spunkie, youthful Tammie."

However, the Bard of Ayrshire suggests he may have misbehaved towards "two truly worthy old gentlemen".

"I am afraid the conduct you forced me on may make them see me in a light I would fondly think I do not deserve," he told Niven.

The meeting between the pair happened weeks after the publication of Burns' first work, Poems Chiefly in the Scottish Dialect.

Despite his later popularity, he cautioned Niven: "Never blaze my songs among the million, as I would abhor to hear every prentice mouthing my poor performances in the streets."

The National Library said the letter, which had been held in private hands since 1899, was an important addition to its collection.

Meanwhile, National Records of Scotland plans to display correspondence providing an insight into how Burns was viewed by his contemporaries.

They were addressed to one of his most important patrons, Robert Graham of Fintry.

The first letter, written by Graham in 1789, describes how Burns, after being told he had been appointed as an exciseman "stood with eyes and hands directed upwards in an attitude poetically fanciful".

The second letter, from 1796, makes arrangements for providing for the bard's family after his death and shows what Mitchell thought of Burns personally.

Graham wrote: "He had certainly many shining qualities, blended with foibles of various kinds, the most irreconcilable whereof were his political principles, which somehow unluckily was rooted, and proves now a drawback to the humane feelings of many, but such a genius as he possessed behoved to have eccentricities of some kind or other."

University of Glasgow lecturer and Burns expert professor Gerard Carruthers said the letters show the poet possessed a "potentially sceptical attitude towards government".