Network Rail has announced details of its bonuses and profits for the last year, but what is Network Rail?
Network Rail owns all of Britain's tracks and other rail infrastructure
Network Rail was set up on 25 March 2002 to buy Railtrack - then the private-sector owner of Britain's railway infrastructure - which it did on 3 October that year.
Railtrack had gone into administration in October 2001 after the government withdrew its funding in the aftermath of the fatal Hatfield crash in 2000.
Railtrack shareholders went to court seeking £157m of compensation, but they failed to convince the judge that then-Transport Secretary Stephen Byers had acted maliciously and actively sought the firm's collapse.
What does Network Rail do?
It owns all of Britain's rail infrastructure, including tracks, signals, most stations, tunnels and level crossings.
It does not run any trains.
Nonetheless, this is not a small organisation - it employs 32,000 staff and owns more than 2,500 stations.
Most of the stations are managed by the rail operating companies, but Railtrack directly manages 17 of the country's busiest stations including King's Cross, Manchester Piccadilly and Edinburgh Waverley.
How is Network Rail different to Railtrack?
Railtrack was a public company with shareholders to whom it paid dividends.
Network Rail is a "not-for-dividend" company, which means that all of its profits are invested in the railway network.
It makes most of its money from track access charges to the rail operating companies.
On top of that it makes money from its property, for example, by leasing space in its stations to shops.
It also receives funding from the Department for Transport and local authorities and it is allowed to borrow money by issuing bonds.
In spite of being a private company, Network Rail produces an annual report and accounts.
It also holds an annual meeting for its members.
Who are the members?
The Department for Transport is a member and then there are rail industry members and members of the public.
The rail industry members include passenger and freight operating companies and rail engineering firms.
The members have the power to appoint Network Rail's directors and auditors.
They are not responsible for Network Rail's strategy, which comes from its Board of Directors.
They don't even get paid - they only receive travel expenses.