In June 1870, "Nedelya" (in Nos. 21–23) published the notes of Alexandra Jacobi, who spent several months with Garibaldi men and was beside Benni all through November 1867. By the time of the Battle at Mentana, Benni has arrived to the Garibaldi camp, as a "Fortnightly Review" correspondent. According to Jacobi, as the 9th regiment commander had been killed, Garibaldi's son Menotti asked Benni to take the leadership upon himself. He did, was injured in the right hand and on 4 November found himself in the Sant'Onofrio hospital in Rome, in the most awful conditions. Alexandra Jacobi, assisted by an English priest, managed to transfer him to Sant'Agata hospital where conditions were better. What appeared to be a slight wound led to the amputation of the right hand, but even this proved to be too late. On 27 December (16 November or 27 November, according to other sources) Arthur Benni died in Rome, from complications of ergotism (according to other sources, gangrene). Two days later he was buried at the Protestant Cemetery, Rome (now Non-Catholic Cemetery), his grave "full of white and red flowers with green leaves, symbolizing Italy's colours", according to Alexandra Jacobi.