This is a story I heard a long time ago and have been trying to find for ages. I've got it now courtesy of The Wanderer, so thought I'd put it here so that it doesn't get lost again.
Dr. Alexander Whyte loved to tell of a commercial traveller named Rigby who, when in Edinburgh, used to stay at the Waverley Hotel, and, on Sunday, always made his way to St. George’s. He could not preach and always found it difficult even to discuss spiritual themes with others. But before leaving the hotel for the church he always looked around for somebody whom he could invite to accompany him. One morning, on approaching a man with this invitation, he received something like a rebuff. The stranger at first refused, but finally consented, and was so moved by the service that he asked Mr. Rigby to go with him again in the evening. That night, at St. George’s, he found Christ. Next morning, in the course of his business, Mr Rigby chanced to pass the home of Dr. Alexander Whyte. Acting on a sudden impulse, he made up his mind to call and tell Dr. Whyte of his experience on Sunday. Dr. Whyte was deeply moved. “I thought,” he said, “that last night’s sermon fell very flat, and I have been feeling very depressed about it. But what did you say your name was?” Mr Rigby repeated it. “Why,” exclaimed Dr. Whyte in delight, “you are the man I’ve been looking for for years!” He then went to his study, and returned carrying a bundle of letters, from which he read such extracts as these: “I was spending a week-end in Edinburgh some weeks ago, and a fellow commercial called Rigby invited me to accompany him to St. George’s. The message of that service changed my life.” “I am a young man, and the other day I came to hear you preach, at the invitation of a man called Rigby, and in that service I decided to dedicate my life to Christ.” Dr Whyte went on to say that twelve of the letters were from young men. of whom four had already entered the ministry.