The Duchess of Cornwall will visit the Trinity Hospice in Clapham later.
Trinity Hospice is the oldest hospice in Britain, and provided care to more than 2,500 people with a range of terminal illnesses last year.
Over 450 of those patients were treated at the charity's inpatient center in Clapham.
The Hospice receives just a third of its income from the NHS, and needs to raise more than £7 million every year.
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Officers were given the touching letter at Brixton Station while they were on a reassurance patrol after yesterday's attack
The 52-year-old had previous convictions for violence but was not on the anti-terror watchlist.
In a statement Charlton Athletic said: Keith was a true hero who will be greatly missed by all the Charlton family and everyone at the club.