Mr. Williamson was originally a printer, and for some time employed in the Courant Office. He became King's Messenger about 1784; and among the first cases of any note, in which he was called upon to act, was that of the celebrated William Brodie, in 1788. After the apprehension of the Deacon in Holland, he escorted him from London to Edinburgh.

On the way the prisoner behaved with much levity of manner, and Williamson used to tell several amusing stories respecting him. While at Amsterdam, Brodie met a Scots woman who asked him if he had been long from Scotland, adding, that one Brodie, a citizen of Edinburgh, was accused of robbing the Excise Office; and that a great reward was offered for his apprehension. In the same city, he became acquainted with the person who had committed a forgery on the Bank of Scotland. "He was a very clever fellow," said Brodie, "and had it not been for my apprehension, I could have mastered the process in a week."

Before arriving in Edinburgh, Brodie was anxious to have his beard cropped, an operation in which he had not indulged for several days. Afraid to trust the razor in the hands of a person in his circumstances, Mr. Williamson offered to act the part of tonsor, assuring the prisoner that he was well qualified for the task. Brodie patiently submitted to the process, which was awkwardly and very indifferenty performed by the man of captions and hornings. "George," said he, as the last polishing stroke had been given, "if you are no better at your own business than you are at shaving, a person may employ you once, but I'll be------if ever he does so again!"

Williamson acquired considerable notoriety in his official capacity in 1793, and subsequent years, among the "Friends of the People," to whom he became obnoxious for his activity as an emissary of the law. Muir of Huntershill, and Palmer from Dundee, were among the first and most distinguished of the Reformers whom he arrested; and when the late Mr. Hamilton Rowan, accompanied by the Hon. Simon Butler, came from Dublin to challenge the Lord Advocate, Williamson was prepared to welcome them, on their arrival at Dumbreck's Hotel, with a warrant for their apprehension.

In the performance of his duty, Mr. Williamson displayed considerable tact and address ; and, without rudeness, was firm and decided. He was a man of more gentleness and humanity than individuals of his profession are generally supposed to be. There are many instances in which he has been known, rather than resort to extreme measures, to have himself paid the debt of the unfortunate individual against whom he had diligence. Being Excise Constable, at that time all the decreets for arrears of licenses were put in force through his hands, under the direction of the late Mr. James Bremner, deputy-solicitor of stamps, to whom he invariably reported all cases of distress. The reply of that good-hearted gentleman usually was—"I leave the matter to yourself, Mr. Williamson; the Government do not wish to make beggars, though they may be fond of the revenue."

In extensive employment, Williamson is understood to have at one time realised a considerable fortune. He lived in the Lord President's Stairs, Parliament Square, but had a country house at Libber-ton, where he and his family resided during summer.