Forgetfulness was not, of itself, a reasonable excuse for possession of an offensive weapon but if related to other factors it could become a defence. Where a judge had allowed such a defence to be raised at trial, to then undermine it made the conviction unsafe.Appeal against conviction with leave of the single judge. On 18 January 2002 at Snaresbrook Crown Court before HH Judge Medwar QC the defendant ('L') was convicted of being in possession of an offensive weapon namely a flick knife. Before the trial L changed his plea to one of guilty on a second count of possession of an offensive weapon namely a butterfly knife. L was sentenced to 12 months' imprisonment suspended for two years. On 19 July 2001 L was stopped whilst driving and his car was searched. A flick knife was found in the glove compartment. L gave a full account stating that he had bought the car a few weeks earlier and whilst cleaning it had found the knife under the seat. L had first thought it was a lighter but after fiddling with it he realised it was a knife. He intended to hand it to police under an amnesty on knives initiative. He put the knife in his glove compartment, he didn't want it indoors as he had young children. L realised it was an offensive weapon but he had forgotten that he had it. His mother had recently died and he was having personal problems. Before the start of trial counsel for L discussed with the trial judge the viability of his defence of reasonable excuse. The judge stated that he did not think L had a reasonable excuse but allowed him to advance the defence. When summing up the judge said that reasonable excuse was a difficult defence to run. It was difficult to see how L could convince the jury that on the balance of probabilities he had had a reasonable excuse for the knife being in his car. After the jury had retired L commented on the adequacy of the summing up. The judge stated that although he had allowed the defence to proceed it was "bordering on the absurd". L appealed conviction on the ground that the judge erred in law whilst directing the jury on the defence of reasonable excuse.HELD: (1) The judge had misdirected the jury on the defence of reasonable excuse. In R v McKellar (1988) 87 Cr App R 372 May LJ held that to forget one had an offensive weapon was not, of itself, a reasonable excuse but if related to other factors it might be a reasonable excuse. (2) However disapproving the judge may have been of the defence raised he had said it could be raised. To then go on and undermine it made the conviction unsafe.Appeal allowed.