Lost towbar keys

My Freelander came with no key to the tow bar, Contacted last 2 previous owners who never had the keys. My husband needs to remove it, it is a detachable swan neck, he thinks it is a Brink or Thule, but is not certain, there are no markings on the tow bar, and no code on the lock. He has found this picture online of an identical swan neck. Can anyone confirm the make, and if taking it to a locksmith is the only option. this number is stamped on the top of the tow ball.
057461
57
ISO 50

Have you tried the Land Rover dealer last stamped in the service book?

Take it to somewhere like these blokes in Lichfield

http://www.all-fit.co.uk/

They'll tell you how to get it off or get a replacement key

Or introduce it to Mr Angle Grinder

Neither Brink, Thule, dealer, or local towbar shop could help, all-fit offered to drill out the lock.
My husbands mate found a key, and it turned out to be to the swan neck.