[NTG-context] Appendix question

[jbf]

A (hopefully) simple question this time:

Why would my appendices be labelled as Appendix One, Appendix Two etc., 
instead of Appendix A, Appendix B? I thought Appendices would normally 
be labelled alphabetically, not numerically.

So I get APPENDIX as the label, I have:

\setuplabeltext
   [en]
   [chapter={\bf Chapter }, appendix=APPENDIX ]

But elsewhere I have:

\setupheads[chapter][indentnext=no,conversion=Words,distance=.25em]

So is that what is affecting my appendices, and if so how do I do it so 
that Chapters get words (One, Two, etc) and Appendices get letters (A,B, 
etc)?

Julian