Two Saturdays ago I was lucky enough to enjoy the unqualified privilege of taking my family to witness not just the most electric sporting moment I have ever seen in person, Mo Farah's second gold-medal performance in the 5,000m, but the awesome Jamaican 4 x 100m relay team break the world record.

As we watched the extraordinary Bolt, Blake and co take their lap of honour, a debate broke out in the crowd around us about the possibility of their having doped like the disgraced Canadian Ben Johnson or the American Justin Gatlin. I absolutely do not believe this to be the case and couldn't believe that people were even raising the subject. But then, I'm an optimist.

For years I chose not to believe Lance Armstrong doped, especially as he never failed a test. Cycling used to leave me cold until I was persuaded to read his extraordinary book, It's Not About The Bike: My Journey Back To Life, detailing his pervasive cancer and the brain surgery, chemotherapy, obsessive training and sheer bloody-mindedness that led him to win the Tour de France (seven times!). I didn't like him, but you had to admire him. Then the remarkable Livestrong campaign made him a total hero to so many.

Now, with his decision to stop contesting doping allegations, and the accumulative weight of so many accusers, sadly it is difficult to still believe in his innocence. It is so demoralising to see heroes crumble before our eyes.

Luckily, I suspect we're about to embrace a whole set of new heroes. See today's Paralympics preview for a guide to so many sportspeople for whom even taking part is an heroic act. If our wonderful Olympic Games proved anything, it's that we have a huge appetite for – deserving – heroes. Bring them on.