Clifford's first post-university job was at Britannia Mines. When he began at Britannia, it was the largest underground copper mine in Western North America. Britannia proved to be a great experience for his young mining career due to the number and variety of mining methods employed there. Cliff was the engineer in charge of the sinking of the No. 8 mineshaft located below sea level.

This was an invaluable experience for him, since mineshafts below sea level have high temperatures and high amounts of raw pressure. Cliffs objective was to school himself in underground mining methods and he was able to do this through exposure as a surveyor throughout the mine. He knew that this experience at Britannia would result in one of the best mining methodology anywhere.

Because of his earlier training with Trail Cominco, Cliff requested and received a transfer to the mine department where he spent nine months as a miner working throughout the mine.
 

In September of 1957, as a result of his experience in mining at Cominco and Britannia, he was able to secure a position of Mine Shift Boss at Denison Mines in the town of Elliot Lake, Ontario.