In 1890 Sir Edward Watkin - a British MP and Chairman of the Metropolitan Railway (now part of London Underground) - held a design competition for the "Great Tower For London" that would have rivaled (or in many cases surpassed) Gustave Eiffel's tower in Paris. In total 68 designs were submitted. You can see a full height comparison of each design by clicking the image above. (created by reddit user herky140).
The Tower was going to be the centrepiece of an amusement park located in Wembley, which would have served as a tourist attraction to lure rail customers out from central London. The winning design would have been 1,200 feet (366m) tall, over 150 feet (45m) taller than the Eiffel Tower. However, the scheme slowly ran out of money and only ever reached a height of 154 feet (47m).
Thus, the tower was nicknamed Watkins Folly and the London Stump. However, all was not lost as Wembley Park turned out to be rather popular. In 1924 the site was picked as the location for the British Empire Exhibition Stadium, better known today as Wembley Stadium.
You can see some of the other proposed designs below: