rather dramatic increase is observed in the fractions of strange particles and baryons, most notably that of strange baryons [@Khachatryan:2011tm]. These observations should not be surprising. The colour flux tubes are expected to have a transverse width determined by the confinement scale, of $\sim 1$ fm. In $pp$ collisions there can be several strings close to each other, and it should actually be rather surprising that models neglecting mutual string interaction are working as well as they do.

Biro *et al.* noted in ref. [@Biro:1984], that the colour charge at the endpoint of a rope formed by strings with random colour charges, is given by a random walk in colour space. The rope can break up in a stepwise manner by repeated production of $q\bar{q}$ pairs, as expected from a local interaction $\propto j_\mu A_\mu \sim
\bar{\psi}\gamma_\mu \psi A_\mu$. This process is analogous to the production of $e^+e^-$ pairs in an electric field. It was pointed out in ref. [@Biro:1984] that for a rope formed by random charges, the number of pairs produced before a total breakup of the rope is in general smaller than the number of initial strings, and also that the total time for this successive split 