Event organisers said it would show the "resistance" to the ban on the group was "stronger than ever".
A man, 37, is arrested in relation to the incident and remains in custody, police say.
The 66-year-old broadcaster is "responding well to treatment", his employer GB News said in a statement.
I Am Maximus wins the Grand National for the second time for trainer Willie Mullins at Aintree - pulling off a feat last achieved by Red Rum in doing so.
Alnour Mohamed Ali, a 27-year-old Sudanese national, was charged with endangering life after two men and two women died.