John Platt was the son of Henry Platt who founded Platt Brothers textile machinery manufacturers in 1770. The company expanded to become the largest supplier in the world. He was the first Liberal Mayor of Oldham in 1854 and served as such at several later dates. In 1865 he was elected MP for Oldham.
He bought the half-built mansion of Bryn-y-Neuadd in 1857, as well as Gorddinog, which he rebuilt for his oldest son. Bryn-y- Neuadd was greatly expanded and improved by him and he was instrumental in bringing great wealth to the village of Llanfairfechan.