Extra police and security staff will be stationed along the route of the London Marathon tomorrow as one of many extra measures being taken by race organisers after consultations with the Metropolitan Police and the Mayor's office.
Increased screening at the registration points for the 37,500 runners has also been introduced after the bombings that killed three people at the Boston Marathon on Tuesday, says London Marathon chief executive Nick Bitel.
The Home Secretary, Theresa May, told MPs more police would be at the Marathon and adjustments to security arrangements had been made.
The Deputy Prime Minister Nick Clegg said everything possible was being done to ensure the marathon passed safely.
In his weekly radio phone-in, Clegg said police had been "double, triple, quadruple checking" arrangements for this weekend's event.