We can do no better than to start with a quote from John Wesley's Journal:
"I preached about noon at Potto and in the evening in the New House at Yarm, by far the most elegant in England. A large congregational attended at five in the morning and seemed to be just ripe for the exhortation - Let us go on and perfection"
April 24th 1764
This was the first time Wesley preached in the completed building, though he had in fact had a great influence in it's design. The earliest records relating to this church concern the plot of land in which it stands. These show that it was conveyed to George Merryweather, a prominent local business man and leader of the Methodists in Yarm on 18th June 1763. Correspondence between Merryweather, Wesley and others lead us to believe that the building was used at Christmas 1763 and officially opened soon afterwards. The Opening service was lead by Peter Jaco, "one of Wesley's preachers", and not by the great man himself, as he was preaching in the Bristol area at that period. Wesley was clearly delighted with the new "House" (that is to say Preaching House, the non conformists were not allowed to call their places of worship Churches) as much favoured the octagonal shape. Altogether 14 octagonal chapels were built by Wesley, but Yarm seems to have been his favourite. The "Large Minutes" for 1780 recommend Yarm as the pattern for such buildings - ''Why should not any Octagonal House be built after the model at Yarm - Can we find a better model?'' Wesley justifies his preference for this particular shape on utilitarian and aesthetic grounds "It is better for the voice and on many accounts more commodious than any other" He is also said to have added - "there are no corners for the devil to hide in"