Update. Marking the base class mutator as protected and using a new Guid property in the sub-class is the closest I've found:

>   public class BaseClass
>    {
>        protected Guid _guid;
>        public virtual Guid Guid
>        {
>            get { return _guid; }
>            protected set { }             //Needs to be R/O
>        }
>    }
>
>     public class Class2 : BaseClass
>    {
>          public new Guid Guid
>         {
>             get
>             {
>                return base.Guid;
>             }
>             set { _guid = value; }
>         }
>     }
>

Any alternative suggestions ?
Viv