The Metropolitan Police say there has been no change London's threat level despite a 40% increase in the number of officers at today's Marathon.
We have worked with organisers, partners and other emergency services throughout the preparations for this year’s marathon to ensure that we have the right plans in place.
Following the terrible events in Boston, we are providing additional visible reassurance to the public in what is naturally a worrying time.
I would stress there is no change to the threat level to London and nothing at this stage to link the Boston bombings to the London marathon.
Nevertheless we want to do all we can to help provide a secure environment in which the runners, spectators and volunteers can enjoy themselves.”
The public are being urged to ensure they take good care of their belongings in order to avoid police responding to reports of unattended items.
London spectators have spoken about their determination to attend this years Marathon- despite events in Boston.
A former professional footballer is aiming to become the first person with motor neurone disease to run the London Marathon.