While still an apprentice, Smirke rode regularly for leading owners, accepting retainers from Solomon Joel, the Maharaja of Rajpipla and the Aga Khan[2] and winning races such as the Chester Cup and the Queen's Vase.

[4] Smirke's ban lasted for five years, during which time he supported himself with a variety of menial jobs, including acting as a sparring partner for professional boxers.

Within a year, he had reached the top of his profession by winning the Derby for the Vijayasinhji Chhatrasinhji, the Maharaja of Rajpipla on Windsor Lad and completing a classic double on the same horse (by now co-owned by Martin H. Benson) with his triumph in the St Leger.

In 1935, he added a second St Leger on Bahram (substituting for the injured Freddie Fox) for the Aga Khan who retained him as his first jockey for the following year.

Despite a difficult working relationship with the Aga Khan's trainer, Frank Butters,[1] Smirke enjoyed further success when winning the 1936 Derby on Mahmoud.

At the outbreak of war in 1939, the Aga Khan moved his horses from Newmarket, but Smirke continued to ride important winners including the St Leger on Turkhan in 1940.

Riding as a freelance, he won the Washington, D.C. International Stakes on Worden and the 1954 St.Leger on Never Say Die (replacing the suspended Lester Piggott).

In 1957, Smirke was riding for the Aga Khan yet again and moved to France where most of the owner's horses were based, but, although he won the 1000 Guineas on Rose Royale, he was unable to establish a working relationship with Alec Head,[1] and the arrangement was soon ended.