  We present a fit of the spin-independent electromagnetic polarisabilities of
the proton to low-energy Compton scattering data in the framework of covariant
baryon chiral effective field theory. Using the Baldin sum rule to constrain
their sum, we obtain
$\alpha=[10.6\pm0.25$(stat)$\pm0.2$(Baldin)$\pm0.4$(theory)$]\times10^{-4}$fm$^3$
and $\beta
=[3.2\mp0.25$(stat)$\pm0.2$(Baldin)$\mp0.4$(theory)$]\times10^{-4}$fm$^3$, in
excellent agreement with other chiral extractions of the same quantities.
