Given the facts as known, it isn't clear that Mr. Grylls' lawyers are NOT in the right.
Actually Mr Grylls lawyers really don't have a leg to stand on, especially if they haven't sent all the other registered trademark owners similar desist letters who ACTUALLY own the 'Bear' trademark.
Bear Grylls Company I believe does not produce knives.
His lawyers should perhaps start here;
Eddie Grylls does own the 'BG Bear Grylls' and the 'Bear Grylls' Trademarks.
http://www.ipo.gov.uk/t-find.htmEdit - To be fair to Eddie, the first he probably knew about was probably the lawyers bull er bill for £5000 for writing the letter by the IP rights specialist at the firm.