Context : Classical novae are eruptions on the surface of a white dwarf in a binary system .
The material ejected from the white dwarf surface generally forms an axisymmetric shell of gas and dust around the system .
The three-dimensional structure of these shells is difficult to untangle when viewed on the plane of the sky .
In this work a geometrical model is developed to explain new observations of the 2015 nova V5668 Sagittarii .

Aims : We aim to better understand the early evolution of classical nova shells in the context of the relationship between polarisation , photometry and spectroscopy in the optical regime .
To understand the ionisation structure in terms of the nova shell morphology and estimate the emission distribution directly following the light-curve ’ s dust-dip .

Methods : High-cadence optical polarimetry and spectroscopy observations of a nova are presented .
The ejecta is modelled in terms of morpho-kinematics and photoionisation structure .

Results : Initially observational results are presented , including broadband polarimetry and spectroscopy of V5668 Sgr nova during eruption .
Variability over these observations provides clues towards the evolving structure of the nova shell .
The position angle of the shell is derived from polarimetry , which is attributed to scattering from small dust grains .
Shocks in the nova outflow are suggested in the photometry and the effect of these on the nova shell are illustrated with various physical diagnostics .
Changes in density and temperature as the super soft source phase of the nova began are discussed .
Gas densities are found to be of the order of 10 ^ { 9 } cm ^ { -3 } for the nova in its auroral phase .
The blackbody temperature of the central stellar system is estimated to be around 2.2 \times 10 ^ { 5 } K at times coincident with the super soft source turn-on .
It was found that the blend around 4640 \AA commonly called ‘ nitrogen flaring ’ is more naturally explained as flaring of the O ii multiplet ( V1 ) from 4638 - 4696 \AA , i.e .
‘ oxygen flaring ’ .

Conclusions : V5668 Sgr ( 2015 ) was a remarkable nova of the DQ Her class .
Changes in absolute polarimetric and spectroscopic multi-epoch observations lead to interpretations of physical characteristics of the nova ’ s evolving outflow .
The high densities that were found early-on combined with knowledge of the system ’ s behaviour at other wavelengths and polarimetric measurements strongly suggest that the visual ‘ cusps ’ are due to radiative shocks between fast and slow ejecta that destroy and create dust seed nuclei cyclically .