Where does the money of British Museum come from?

Everyone has heard of British Museum; as a free-entry museum with 5.5 million people visiting yearly, with no doubt it needs a large amount of money to sustain its running. Where does this money come from?
Let’s talk about the background first. The British Museum is a “non-departmental public body” partly sponsored by the Department for Culture, Media and Sport (DCMS) (British Museum). There is an agreement for a three-year funding.  A board of twenty-five trustees, with a Director, is managing the museum including its finance.
It is notable that the funding by DCMS is not solely dependent on the visitor number, but also depends on whether the museum can meet the performance target agreed. For example, DCMS will access the number and categories of visitors, and its self-generated income, its increased virtual access to collections, longer opening hours, and number of outreach projects.
There is an increasing need to obtain more money as the museum is aiming to develop an e-strategy and easier access of building for public. The expenditure budget for the British Museum in total for the year 2001/2, is expected to be £46 million whilst the grant from the DCMS for the year 2001/2 is £36 million. In other words, deficits are recorded in their annual accounts (BBC).
(Expenditures of the museum are spent respectively in education department, operations such as security, information technology and building management, marketing and public affairs, and fundraising events)
Seeing the great expense in the future, the museum also needs to gather constant private fund grant from different parties in the use of buildings, acquisitions and others. Recently there is a Heritage Lottery Fund grant of £10 million for World Conservation and Exhibition Centre (WCEC) that will be completed in 2014 spring (British Museum). Besides, it also received the donation from the Sainsbury’s family – which valued at £25 million for building a gallery in North Wing.
It also obtains funding from revenue-raising activities such as “onsite retail” (£2.48 per visitor), catering (£0.9 m), corporate hire, sponsorship income (£1.7m), Great Court trading (£30m from Millennium Commission, £15.75 from Heritage Lottery Fund), Friends’ organisations (£5.6 m) and also through patrons and donors schemes (£0.15m)”(BBC).
So British Museum is striving hard to make ends meet; but there is good news from the UK government. it will be benefitted from an amended tax law by the government that allows the museum to recover an amount of £1.2 lost in VAT. More flexibility in annual budget, and other investment plans would be allowed to carry out!