According to this 1970's Denis Wick leaflet the cornet mouthpieces were designed in association with Thomas Wilson, principal cornet player with the Scots Guards:
Here is a web page which tells you all about Tommy Wilson, who emigrated to Canada and also performed as a soloist with the Salvation Army:
In the early 1970’s I was asked by Denis Wick if I would help him develop a cornet mouthpiece – and the rest, as they say, is history. It was also round about this time I was asked by Boosey & Hawkes if I would help in the development of a new cornet for them. After a lot of hard work the first large bore Sovereign cornet was born. I still play the original prototype. It’s still going strong after over 30 years. It was stamped No. 1, (which causes the customs people more than a little curiosity when London Citadel Band goes on trips).