DB also knows he could depart sans Radar but had to have his Decca in the old days and I am comfortable that might hold yet today but with some restrictions now that the miracle of GPS is with us.
Radar is a very nice thing to have but it is not a necessity.
That being said I would have gladly launched without the Decca if I had the Radar which I consider an electronic eyeball that sees through cloud, rain, snow, and fog and most importantly is User Friendly compared to the Decca Products.