Boston tech giant Hale and Dorr and Washington DC’s Wilmer Cutler & Pickering are merging to create a 1,000-lawyer US titan in the latest mega-merger to hit the American market.

The new firm, which goes live on 31 May, will be called Wilmer Cutler Pickering Hale and Dorr and will create a top 10 US firm by revenue with a combined 2003 fee income of almost $700m (£390.5m).