Phase 2: Randomisation The assistant will code the participants so that the researcher who will run all the statistical analyses cannot identify the participants. After the participants are coded, the researcher will randomise the coded participants into two allocation groups. A blocked randomisation process will stratify the participants according to three child factors (sex, age and child behaviour difficulties). A computerised random integer generator will be used to generate the random allocation sequence for the separate randomisation lists. A sample size calculator formula for statistical superiority design indicated that 130 participants would be required to achieve an effect size of 0.8 for the primary outcome measure at the 5% significance level with a ratio of 2:1 intervention to control. After we allowed for expected drop out of 40% based on similar studies (Sanders, Prior, & Ralph, 2009) the target population was 182 parents. After initial randomisation, the same process will be followed for every additional person who is interested in participating in the study. The assistant will include these participants in the appropriate group.