Reynolds Porter Chamberlain (RPC) has sent senior associate Umayya Abu Deeb on an emergency secondment to publishing house Bloomsbury to protect the secrets of the last Harry Potter book before its launch.
Defamation and IP partner David Hooper is leading the team from RPC's City base. He said: "Not to spoil the fun for the children is what it's all about."
The firm also helped out on the launch of the fifth and sixth Harry Potter books, getting an injunction to stop stolen extracts of the books appearing in the press.
This time, the internet has posed more challenges.
Hopper said: "There haven't been the thefts of the book that there were before. But the main change is policing the internet has become much more complicated."
Long-time RPC rival Schillings is acting for Harry Potter creator JK Rowling.
Even the lawyers have been unable to get a quick peek. Hooper said: "My children will be buying it at 12.01am, like everyone else."