ST_Within not returning any records

[HarryClarke]

I have a simple table of points, which I want to view only those those points within a Polygon, and exclude those points outside of the polygon. The polygon is defined in a view that only contains the one polygon (actually VC17 - Surrey). If I issue in the WHERE clause the condition tetrad_records.the_geom && vc17.geom

I get the expected result (i.e. only those points in the bounded box defined by the polygon. However, if the WHERE clause is (or any variant) ST_Within(tetrad_records.the_geom,vc17.geom)

no records are returned. Ditto for ST_Contains and variants. Is this something I am doing wrong, or is it a bug. PostGis version 2.1.3 running under Windows 8.1 - 64 bit, and PostgreSQL 9.3.5

[HarryClarke]

Problem resolved