Slaughter and May and Latham & Watkins have scored the top advisory roles on Canadian buyout firm Onex Corp's acquisition of Swiss packaging group SIG Combibloc Group for up to €3.75bn (£2.98bn).

Onex, the largest listed private equity firm in Canada, will stump up €3.57bn (£2.84bn) upon completion of the transaction, with an additional amount of up to €175m (£139m) payable depending on the financial performance of SIG's business in 2015 and 2016.

The deal is awaiting regulatory approval and expected to close in the first quarter of 2015.

Latham advised Onex on the transaction with a team led by London corporate partner Mike Bond, London finance partner Jay Sadanandan and Washington DC capital markets partner Rachel Sheridan, alongside Munich corporate partner Kilian Helmreich and London corporate partner Tom Evans.

Bar & Karrer partner Thomas Rohde was also instructed to advise Onex on Swiss law issues.

A Slaughter and May team led by corporate partners Mark Zerdin and Nigel Boardman (pictured) acted for SIG owner Reynolds Group Holdings, the American packaging company backed by New Zealand's richest man Graeme Hart.

It is understood that Debevoise & Plimpton provided advice to Reynolds Group on anti-trust matters, and that Onex beat off the challenge of private equity rival Partners Group to secure the acquisition.

Based in Neuhausen am Rheinfall, Switzerland, SIG has annual earnings of around €420m (£334m).