''If my memory serves me correctly DB claimed the longest single sector trip on the VC10 at B.U.A. with a charter from Gatwick to Beira in Mozambique for an oil company''
Much longer flights have been done by VC10s since - I done more than one myself. In fact, I'm sure the VC10 still holds the record for a direct flight between London and Sydney.
Of course, Air to air refuelling helps!