Tens of thousands of runners have taken part in the London Marathon, many with black ribbons on their vests in honour of the victims of the Boston bombings. Hundreds of extra police officers were drafted in as part of an effort to step up security.

Seconds of silence in tribute to the victims of the Boston bombing…

Silence: London runners pause to remember the terrible events in Boston, where bombs killed three people and injured more than 100.

Inevitably, as the runners teemed over the marathon start line in bright spring sunshine, there remained clouds of doubt hanging in the air.

"I was always going to run today but obviously, after what happened, it was so shocking and sort of terrible to see, so it does run through your mind - Is the same thing going to happen here today?"

"Quite worrying obviously and a bit nervous about it."

The competitors were wearing black armbands.

London's Metropolitan Police had almost doubled the number of officers and sniffer dogs sent out to secure the event, saying this was to reassure the public and not in response to a specific threat.

In the Skies above the British capital, a police presence also looked on.

Along the entire 26 mile route from leafy Greenwich to the Tower of London, Big Ben and Buckingham Palace, litter bins had been removed as part of the enhanced security.

For every one of the 36,000 runners who successfully crossed the finish line, the marathon organisers promised a $3 dollar donation to One Fund Boston – a total of more than $100,000 dollars.

But the best news was that as runners passed the finish line in London, the glorious day's sunshine was matched by the success and safety of the event.

They'd paid tribute to their fellow runners in Boston, raised hundreds of thousands of dollars for charity and taken part in a vast, colorful and often amusing spectacle.