Private function in the derived class is getting called with base class pointer

Question

My Code looks like this -

#include <iostream>
using namespace std;

class Base {
    public:
        virtual void print() {};
};

class Derived: public Base {
    private:
        int secret;
        void print() {
            cout<<"the secret is "<<this->secret<<endl;
        }
    public:
        explicit Derived(int a): secret(a) { }
};

int main() {
    Base* b1;
    Derived d1(1022);
    d1.print();   // Wont Work - and should not work 
    b1 = &d1;
    b1->print();  // Works and prints the secret
    return 0;
}

I don't understand how can a derived class private function be called using a base class pointer? I understand that after declaring the base class function as virtual we essentially use late binding and check the contents of the pointer before associating it with a function call but does it ignore the access specifiers in the derived classes if the base class implementation of the same function is virtual and public?