Using the best available experimental data and lattice calculations of scattering lengths of 𝜋𝜋
scattering and employing dispersive representation of the amplitude based on Roy equations,
we compute the subthreshold parameters of this process. We use Monte Carlo sampling to
numerically model the probability distribution of the results based on all uncertainties in the
inputs. In the second part of the analysis, employing Bayesian inference, we use the new results
for the subthreshold parameters to obtain constraints on the leading order low energy constant 𝐵0
in the context of three-flavour chiral perturbation theory.