PC Marc Horsewood from Lincolnshire Police speaks to ITV News about the importance of the march in London.
He is just one of up to 20,000 police officers from forces across England and Wales travelling to London today.
This is the first police march in the capital for more than four years.
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His family are extremely worried as they say this is really out of character for Aaron who has never been missing before.
Very mild but often cloudy and damp.
Mostly dry but rather cloudy overnight. Turning windy Monday morning.