The annual supplement free with The Sunday Times on 26 April is believed to have helped the market-leading quality title achieve a circulation in excess of 1.3 million.
Though the figure is not officially audited, sources claim it topped the previous week's issue that recorded an estimated circulation of 1,175,000 copies.
However, it is believed The Sunday Times' biggest circulation spike this year came courtesy of the Noel Gallagher CD giveaway, in March, which added 170,000 to its circulation.
The personal fortunes of the UK's wealthiest media moguls have been slashed by more than £3bn, according to the Rich List.
In recent years, The Sunday Times has switched emphasis away from promotions to retaining loyal readers, promoting its subscription services, although it still uses giveaways as a marketing tool.
The Sunday Times, which became Britain's first £2 newspaper in September 2006, recorded an ABC average figure of 1,240,348 in March this year, a slight dip of 0.02% year on year.