Freshfields Bruckhaus Deringer and Linklaters are advising on Babcock & Brown's planned £3.5bn acquisition of Angel Trains from the Royal Bank of Scotland (RBS).

Both firms are advising regular clients on the transaction, which is still to be formally announced, with Babcock turning to Freshfields and RBS to Linklaters.

Freshfields corporate partner Richard Phillips is understood to be leading the team for Babcock, while Linklaters corporate partner William Buckley is thought to have the lead role for RBS.

Buckley regularly advises RBS and has previously advised the bank on its disposal of Southern Water to a JP Morgan-led consortium in 2007.

Babcock uses a variety of law firms and, besides Freshfields, has previously instructed firms including Clifford Chance (CC), Milbank Tweed Hadley & McCloy and Mallesons Stephen Jaques in Australia. Last year CC took the lead role for Babcock on a €1.03bn (£700m) refinancing of its wind farm portfolio, while Freshfields acted for the lead arrangers.

Angel Trains has been up for sale since September last year, with Babcock thought to have secured the deal through a debt package backed by a group of lenders including Deutsche Bank.

The disposal came after both Linklaters and Freshfields secured roles on RBS's record £12bn rights issue, announced last week.

Linklaters banking chief Robert Elliott is leading the team for RBS alongside corporate partners Matthew Middleditch and Anne Drummond and US corporate partner Tom Shropshire.

Freshfields, meanwhile, is advising the underwriting banks – Goldman Sachs, Merrill Lynch and UBS – with corporate partners Simon Witty and Sarah Murphy leading the team alongside financial institutions group co-head Will Lawes.

Both the rights offering and the Angel Trains deal come as RBS prepared to announce writedowns of £5.9bn in subprime-related assets. It is thought RBS is also planning to dispose of its insurance arm, which includes Churchill and Direct Line. The companies could have a price tag of between £4bn and £5bn.

Commenting on the rights offering, Elliott told Legal Week: "What is so complex here is that it is very difficult to estimate the amount of writedowns. The reality is that other British and European banks may have to follow suit."