Not sure where you are with Allan Lea but consider this.
I found a Mary A Butler on a passenger list to Quebec City date 1873/10/03 with her family (Father William mother Mary) and siblings. She was 15.http://www.collectionscanada.gc.ca/databases/passengers-queb...
If Mary Ann was in Canada, or on route, and became pregnant with Allen to William Lea or another, could she have been shipped back to England to be married and become respectable. The child would have been b. Canada but a British citizen, the child may have been Allen Butler initially