1. A liquid flow assay for detection of a target analyte in a liquid sample wherein the liquid sample flows through or along a test strip or sheet comprising a porous material and said test strip or sheet has a detection zone for said analyte wherein said analyte is detected by a specific binding assay of a sandwich or competitive format, characterised in that: said detection zone is a single combined analyte detection and control zone wherein any target analyte is contacted with a first labelled reagent and a second labelled reagent provided as mobile reagents and carrying detectably distinguishable labels, and wherein both said first and second labelled reagents are components of the specific binding assay for target analyte, one of said labelled reagents additionally carrying a first member of a specific binding partner pair which binds to the second member of said pair immobilised in said detection zone, said immobilised second member of said specific binding partner pair not binding target analyte, whereby irrespective of whether said sample is a positive or negative sample a captured label signal is detectable in the detection zone, positive and negative samples being distinguishable by detection of different captured label signals.