He is a science graduate of the University of London in 1976. He is now an International ultra distance runner and has the distinction of having won his debut races at 100 km, 24 hours, 3 Days, Six Days,  7 Days and 8 Days. He was world number one for the Six Day event in 2006 and has represented Great Britain eleven times since 1996. He is a former British 100 km champion, world 100 km champion for his age group, and world record holder for treadmill endurance. Since 1982 he has lived on the Orkney island of Sanday.
He won the Monaco Six Day race in 2006 and 2007, and also in 2006 came 7th in the 135 mile (216 km) Badwater Ultramarathon in Death Valley, California in a record time for a British runner, becoming the first Scot to complete the event . In 2007 he became the Scottish 48-hour record holder, and achieved the best British performance since 1998 in the Spartathlon in Greece.
In 2008 Sichel set an All-Time Scottish 6 Day track record of 857.070 km/532.56 miles when winning the Hamm 6 Day race in Germany.
In the Athens 1000 Mile World Cup race held in March 2010 Sichel was runner-up in an age-group world record of 13 days 20 hours, 8 minutes and 1 second. Average of over 72 miles (2.8 marathons) a day. Sichel became the oldest British person ever to have completed a 1000 miles in under 16 days. He also set intermediate age-group world records at 6 Days and 1000 km. The last time a British male runner completed a 1000-mile race, in under 16 days) was in 1991.
In May 2011 Sichel set an overall 6 Day Great Britain road record of 834.190 km/518.34 miles when winning the International 6 Day road race in Balatonfured.
In the Monaco “No Finish Line” 8 Day race in 2011 (which had over 6,000 participants) Sichel won the event outright, set a new course record and became the first person to cover more than 1000 km during this event.
In 2014 Sichel competed in the World's Longest Certified Footrace - the Self Transcendence 3100 Mile race in New York. He finished in  50 days, 15 hours, 6 minutes and 4 seconds becoming the  first person from Britain to complete the event inside the 52-day time limit] and also the  first person aged over 60 to finish the race since it started in 1997.
- "Heat is on for Death Valley endurance racer". The Sunday Times. London. 2006-07-23. Retrieved 2008-02-11.
- "Paisley Students Aid Record Breaker". University of the West of Scotland. Retrieved 2008-02-15.
- Russell, Fiona (2006-10-08). "DESERT BRAVEHEART; SCOT RUNS IN TOUGHEST RACE IN THE WORLD - 135 MILES THROUGH DEATH VALLEY". Daily Record. Retrieved 2008-02-15.
- "Athlete's Death Valley 'triumph'". BBC News. 2006-07-30. Retrieved 2008-02-11.
- "Citizen of the Year". Orkney Today. Retrieved 2008-02-15.
- Wallace, Andrew (2003-09-26). "Athletics: Marathon man Will Scotland's very own Forest Gump; Sichel has already beaten cancer .. now he's on the run for 24 hours". Daily Record. Retrieved 2008-02-15.
- williamsichel.co.uk, Personal website