Cliff Arnall, the psychologist who ‘calculated’ that Monday is the most depressing day of the year is urging Britons to “refute the whole notion” and be cheerful instead.

The third Monday in January became a black day in 2005 when Mr Arnall was paid by a public relations firm to identify the most miserable date in the calendar in order to promote holiday firm, Sky Travel.

The former part-time evening psychology tutor at the adult education unit of Cardiff University has since set up his own ‘happiness consultancy’ called No Pills offering conference presentations and two-hour courses on motivation in Brecon Cathedral for £50.