Virtual Functions Object Slicing

My question is with reference to this question which explains how virtual functions work in case of object slicing which end up calling base class virtual function and Wikipedia article which explains the virtual table layout for a derived class for below code

    class A{

    public:
     virtual void func(){ cout<<"\n In A:func";}
    };

    class B:public A{

    public:
     virtual void func(){ cout<<"\n In B:func";}
    };

   main(){
    A *ptr1 = new B();

    A oA = *ptr1;

    oA.func(); 
  }




      DerviedClassObjectB:
         +0: pointer to virtual method table of B 

       virtual method table of B:
         +0: B::func

Above program outputs "In A::func" .

But how does without virtual table for class B knowing about base class A::func ends up calling A::func