A method of assessing for a mobile terminal 1 the suitability of a cell of a cellular telecommunications network includes measuring the radio signal at the mobile terminal 1—step A; and calculating at least one of a first mean value of a plurality of the radio signal measurements over a first time period—step B—and a second mean value of a plurality of the radio signal measurements over a second time period, longer than the first time period—step D. Two different thresholds are provided. The or each mean value is compared to one or respective ones of the thresholds—steps C and E. If the or either of the mean values are below the or the respective threshold, then this indicates that the cell might not be suitable for the mobile terminal. In that instance, a cell reselection process—step F—or a cell handover process can be triggered. By providing two mean values and two different thresholds, it is possible to provide improved sensitivity to variations in the radio signal as a result of the mobile terminal moving quickly within a cell and less sensitivity to fluctuations of the radio signal at a mobile terminal that is substantially stationary and which are due to “fading”.