But Bristol to Florence is quite within its capabilities. Its not like there's a short departure runway as there is at LCY earlier in its day's rotation.
Back in the supposedly "bad old days" of IT flights at least the various flights were carried out, maybe late if the inbound was so. If there happened to be insufficient performance on the day (like One-Elevens operating to Tenerife) then a fuel stop was arranged. But this is only 725nm, less than half the E-170s typical max payload range.