Evolution of the perihelion distance (plot a)); semi-major axis b); eccentricity c); argument of perihelion d); longitude of ascending node e); and inclination to the ecliptic f) of the orbit of comet 12P/Pons-Brooks (thick red curve) over the past 35.5 millennia. The corresponding evolution of the orbital elements of 100 cloned orbits (dashed green curves; see Sect. 3) is also shown.