As trade talks with the European Union started to flag in June, Boris Johnson borrowed a phrase from a series of 1950s gasoline ads, promising he would "put a tiger in the tank” to rev up the negotiations.

As September approaches, it’s clear that engine has stalled. The negotiations now risk ending in failure.

The latest round of discussions in Brussels wrapped up this week without any progress. Both sides agree that on the most difficult topics — access to British fishing waters and how closely the U.K. will stick to EU rules on state aid — there has been virtually no movement since the process began in March.