We have used optical microscopy and multiple-beam interferometry to study the phase behaviour of n-octadecane (n-C 18) confined between mica surfaces in the vicinity of and below its bulk melting point ( T m=28.2°C). n-C 18 adsorbs from vapour (relative vapour pressure p/ p 0≈0.97) to an isolated mica surface, forming 2.8±0.2 nm thick film. At a separation between two mica surfaces of 11±1 nm capillary condensation occurs, and liquid n-C 18 fills the gap between the surfaces and pulls them into contact, both above and below T m. The condensate does not freeze down to Δ T=14°C below T m while the surfaces are in contact, although slow growth of crystals from the liquid into the vapour phase occurs for Δ T≥5°C. At an isolated surface, e.g. after separation of the surfaces far enough for the liquid condensate to snap into two droplets, freezing occurs readily at all temperatures below T m. As the temperature is lowered, freezing of bridging necks of liquid between two surfaces starts to occur at progressively smaller surface separations. Finally, for Δ T≥5°C, freezing may occur during separation, as the surfaces come apart. The observations can be rationalised by comparing variations in the condensate volume to variations in the interfacial areas (n-C 18 mica and n-C 18 vapour). In general, the mica-condensate interface prevents freezing, while the vapour-condensate interface appears to promote nucleation of solid. The results are in accord with the idea that proximity to a crystalline surface like mica leads to a very large melting-point depression for any wetting liquid.