The last time this many police officers hit the streets of London it was to quell the worst disturbances in England for a generation.
It took 16,000 - exactly the same number of officers who will be lost as a result of Government cuts to policing over the next four years.
That is just one of the issues facing policing which has brought out the rank and file to protest against what they claim is an unprecedented attack on policing.
Many fear these cuts are putting the public and themselves at risk and pour scorn on Home Office claims that the 'frontline' remains unaffected.
All are angry at significant changes to their terms and conditions such an increasing already hefty pension contributions and removing payments in some cases worth thousands of pounds a year
They reason that with a public sector pay freeze in place they are being asked to do more work in return for less pay and disciplined if they fail fitness tests.
Their leaders in the Police Federation say morale has never been lower and the comments on social media suggest that is true.
Many of those marching today do not support the suggestion that police should have the right to go on strike (it's been illegal since 1919).
But their fury at the reforms to their pay and conditions suggested by Tom Winsor can not be underestimated and they suspect it's their inability to withdraw their labour which has made them an easy target for ministers in an age of austerity.
They've been angry too at the perceived lack of support from their chief officers who they believe support many of the proposals.
Just one chief constable will be marching with them - Gloucestershire's Tony Melville who announced his resignation in protest at the Winsor Review and plans to make chiefs answer to directly elected US-style commissioners.
On duty 24/7, they're used to being battered, bruised and unloved - just not by those who they thought were on their side.