  We present the current status of our lattice calculation of the
electromagnetic form factor of the pion with two flavours of non-perturbatively
O(a)-improved Wilson fermions. Using twisted boundary conditions and stochastic
sources we obtain accurate results with a fine momentum resolution near
$q^2=0$. This enables the computation of the charge radius without model
dependence. The ensembles cover various lattice spacings and pion masses,
ranging down to 250 MeV. This allows to compare the data to continuum chiral
perturbation theory to NNLO including corrections of finite lattice spacing to
perform a simultaneous chiral and continuum extrapolation. An estimate for the
systematic error resulting from the extrapolation can be obtained by looking at
the spread of results obtained from other functional forms such as polynomials.
