The service will be a "tremendous celebration" of the duke's life, the head of the armed forces says.
The Duke of Edinburgh oversaw modifications to the car, which will carry his coffin at Saturday's funeral.
The health secretary is accused of "cronyism" but the government says he acted "entirely properly".
Lord Kerslake says links between Greensill Capital and the government must be "thoroughly investigated".
The Scottish government says the lockdown changes are designed to help reunite families and close friends.