They first encountered the stuff in 1906. Holmes despised it. Watson loved it - just why, Holmes never understood, but soon Marmite became a running joke.
Watson would bring some to Sussex, Holmes would insult it, and Watson would return to London with it.
In 1919 Marmite appeared at Holmes's tea-table. Watson glanced at it and repressed a shudder.
"It was part of our daily rations," he admitted when Holmes pressed him.
That night the Marmite was solemnly buried in a Sussex garden, and was never referred to again by either gentlemen.