Campaigning group Families Fighting for Justice has organised the meeting. Here's how they describe the event on their anti-crime Facebook group:
"We have organised a massive march a few days before the general election in London. We want every organisation and individuals to come together as one. Knife crime, gun crime no matter what.
"We will be shouting for 'life to mean life' for murder and manslaughter. Please now is the time to make your voice heard you must join us for the mother of all marches to stand together and say STOP STEALING OUR CHILDREN, we want Justice we want the respect for human life to be put back also the deterrent to then make this country be a country to be proud of as it once was.
"We want as many of you to gather within your own communities to arrange this trip to London - the more voices there the better. The message will be put across, united we stand. It is no good just thinking what is wrong but to do something about what you think and know to be true. All carry your loved ones photo with you, or the name of your organisation, or just come along as you are, wear t shirts with your loved ones photo on. Show we have had enough.
"Do not wait for it to knock on your door before you do anything because then it will be too late for you and your family, we do not want anymore families in this dark place where we are now.
"We need all of your actions putting into words - we need the masses to march and show we are a country who will stand united, united for peace.
"So we do not have much time as we want to march before the election so get going on getting together to meet.
"We will be meeting at the Victoria embankment nr the Temple tube station at 2pm. and walking to Westminster. There, a guest speaker and other speakers (families of murder victims) will say a few words.
"We are meeting up afterwards at the Novotel hotel, Kings Cross road (five mins away from Euston) for a drink or two, everyone welcome."