There can be no reason for blue light convoys to exceed the speed laws.
Three reasons may exist as to why the vip should travel at speed.
1. The VIP needs urgent medical attention for some reason.
2. The VIP needs to be protected from hostile acts along the road. Hello! When last did we have armed gunmen firing at motorists much less politicians? Not even the ANC could get that right prior to '94.
3. The VIP is late!  So what.
This is a trick learnt from foreign police types which in RSA there can be no justification at all.
Big man syndrome.