Even as its Worldwide division was producing its most successful year, about to be further boosted by Dr Who episodes available on Facebook, the BBCís latest accounts show the extent of the corporationís challenges in controlling costs.

In the 12 months to 31 March 2011, BBC Worldwide grew headline sales by 7.8% year on year to £1157.7 million, with international sales increasing by 9.6% to 55.5% of total headline sales as the business sharpens its focus on international markets.

Such revenues were at the heart of a 10.3% surge in profits to £160.2 million, the highest level ever for the division. Profits before tax were given a fillip by the sale of channel to former partner Discovery in November 2010. However, the bottom line was an 8.6% increase in the overall return to the BBC to £181.9 million.

Digital products scored, predominantly online and mobile, for which the corporation as a whole has huge hopes for with an array of smartphone and tablet products, scored well for the division, accounting for 8.1% of net sales. Flagship online property BBC.com saw revenues increase by 113% in the US alone, and in the year ahead, Worldwide will benefit from the launch of pilot a global BBC iPlayer, a bigger games portfolio and more mobile services and apps.

Among the most popular current apps is that for Dr Who was which the top selling international programme title. And the Time Lord is all aboard the Tardis to make a further contribution in a new venture which will offer immediately a series of digitally remastered Doctor Who stories to Facebook users in Europe, the USA, Canada, Australia and New Zealand. By using Facebook credits, users visiting the official Doctor Who page will be able to stream a selection of nine stories (each containing several episodes) from the history of the programmes which began in the early 1960s. Once rented, episodes will be available to view for 48 hours.

Yet despite the good news from BBC Worldwide, the corporationís general mood of the day was tempered by a warning from BBC Trust Chairman Lord Patten underlining the challenges facing the BBC as it works to implement last year's licence fee settlement. "As well as stretching efficiencies, this will mean some tough choices - the Trust is clear that the BBC must retain distinctive and high quality content in areas that matter to audiences. We're working hard with the Executive on the detail of how the new licence fee will be implemented, and will share these plans with the public as soon as possible."

Over the course of the financial year, the BBC revealed that it delivered £434 million in efficiency savings, meeting existing targets for 3% efficiencies, and adding up to over £1 billion of savings since 2008/09. The BBC claims that it is making progress in reducing the senior manager pay bill, and is on track to deliver 25% savings and a 20% reduction in headcount by the end of this year. Yet even though the BBC's overall costs on personnel dropped by £9 million to £213 million in the year, thanks mainly to key presenters leaving the corporation, the cost of relocating key departments to the new base in Salford added £15 million to the overhead bill of £421 million.