Anna Kennedy from Hillingdon was at Buckingham Palace to receive an OBE from the Queen for her campaigning work to help her two children, one has autism, the other has Asperger's Syndrome.
She had also helped other youngsters with those conditions.
As part of her work over the years she has opened her own school.
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The 20-year-old was found fatally wounded on Roth Walk, near Finsbury Park, north London at around 3am on Saturday, Scotland Yard said.
Police have arrested a man wanted in connection with a burglary at the home of pensioner Richard Osborn-Brooks.
The rally comes after it emerged that the Home Office destroyed thousands of landing cards documenting the arrival of windrush-era migrants