We present time-resolved optical spectroscopy of V458 Vulpeculae ( Nova Vul 2007 No .
1 ) spread over a period of 15 months starting 301 days after its discovery .
Our data reveal radial velocity variations in the He ii \lambda 5412 and He ii \lambda 4686 emission lines .
A period analysis of the radial velocity curves resulted in a period of 98.09647 \pm 0.00025 min ( 0.06812255 \pm 0.00000017 d ) which we identify with the orbital period of the binary system .
V458 Vul is therefore the planetary nebula central binary star with the shortest period known .
We explore the possibility of the system being composed of a relatively massive white dwarf ( M _ { 1 } \gtrsim 1.0 ~ { } \mathrm { M _ { \odot } } ) accreting matter from a post-asymptotic giant branch star which produced the planetary nebula observed .
In this scenario , the central binary system therefore underwent two common-envelope episodes .
A combination of previous photoionisation modelling of the nebular spectra , post-asymptotic giant branch evolutionary tracks and the orbital period favour a mass of M _ { 2 } \sim 0.6 ~ { } \mathrm { M _ { \odot } } for the donor star .
Therefore , the total mass of the system may exceed the Chandrasekhar mass , which makes V458 Vul a Type Ia supernova progenitor candidate .