I helped Gordon Brown prepare for TV debates in 2010. How did the two leaders come out of Tuesday night?

The YouGov snap poll scored it neck and neck—51 per cent thought Boris Johnson had done better, 49 per cent thought Jeremy Corbyn had. Both sides will be happy with that. Last night was the first ever head-to-head TV election debate between a PM and the leader of the opposition. What did we learn?

Incredibly, Johnson had not learned his lines. For both the opening and closing statement, he kept glancing down to read his pre-prepared remarks. Not only does this look less convincing than someone looking you in the eye and telling you what they believe, it also suggests a degree of complacency. This is the most important job in the country, the least you can do is learn your arguments off by heart.

Time after time, Johnson talked across Julie Etchingham. In rehearsals, his team would have tried to coach this out of him. Doing it once is fine but doing it repeatedly is a bad look. It is the kind of subconscious behaviour that viewers pick up and judge: this man does not think the same rules apply to him as everyone else. Given it is Johnson’s nature to ramble on, I thought Corbyn could have prepared some lines to pick up on that and attack it. After all, failing to meet the deadline is one of his big policy failures.

Normally one would expect the incumbent, especially if they were 10 points ahead in the vote intention polls, to be the one who would rise above the political fray and the challenger, desperate to catch up, to be the one who went most on the attack. However, this time the roles were reversed. Johnson was much more aggressive than Corbyn.

Overall Johnson’s team will feel he came through it unscathed. There were no questions on the alleged affair with Jennifer Arcuri, or about his own children: a bullet dodged.

Initially, Corbyn’s voice seemed a little weak and he appeared tired. The lens in his glasses reflected the glare of the light in the studio in a way that made it hard to see his eyes clearly. This may seem trivial but eye contact is important: it helps you judge whether a stranger is sincere. If it is possible to change the glasses, the lighting or camera angle to avoid that effect, his team should consider it for future debates. It is possible to work with the broadcasters to avoid these minor problems: when we were preparing for the multi-party TV debates in 2010, we worked with the studios to ensure that Gordon Brown would be able to see his opponents, the presenter, and the audience despite his restricted field of vision (he is blind in one eye from a school rugby injury).

Perhaps Corbyn’s weaker first half was merely nerves, because he grew into the performance as the evening wore on. As the questions moved to domestic policy, Johnson appeared to be the one who was weaker and that was reflected in the IpsosMORI tracker of social media sentiment, which saw Johnson’s scores dip the longer he spoke. Corbyn was bright, funny and sharp on the quickfire questions. His response to the question about the Royals (“needs improvement”) was probably the best of the night from either of the candidates. (His response to another question, about a potential coalition with Nicola Sturgeon, was also a highlight: we’ve had nine years of chaotic coalitions already, he said without hesitation.)

Corbyn’s one big moment should have been his answer to the question on NHS. He could have let Johnson waffle on and then with a flourish waved in his hand the redacted notes of the meetings between US big pharma and the UK government as proof of the Conservatives’ secret plans to privatise the health service. In rehearsals, this is presumably what they practised and the effect would have been terrific. But instead Corbyn played his card too early and in response to a question on Brexit, allowing Johnson to rebut the claims as a smear to distract from Brexit.

What made this debate a more rumbustious political knockabout than previous leadership debates was partly the willingness of the prime minister to go on the attack, but even more it was the reaction of the audience to both men. Again and again, the audience laughed out loud at the contestants (and only occasionally with them). They laughed at Corbyn for suggesting his position on Brexit was “clear” and for a fumbled answer on a four-day week. They laughed at Johnson—perhaps more significantly—when he said “yes” to Etchingham’s question on whether trust matters. They laughed at him when he said he would deliver on his promises. And they laughed at both for what Etchingham called out their magic money tree.

Over the course of the evening, the IpsosMORI tracker showed a marked decline for both men. Jo Swinson would have been frustrated to have sat this one out, only allowed to appear in a secondary leaders’ debate later in the evening. But given the derision these two brought upon themselves, her absence this time may make the impact of her appearance at the BBC’s seven-way debate much more powerful.

Neither Johnson nor Corbyn really seemed prepared for how much leeway Etchingham was prepared to give them to challenge each other. By and large, they waited for her questions or those from the audience but from the start, she made it clear they could go straight at each other. I was surprised they hadn’t prepared more direct “yes or no” questions for each other.

Johnson had everything to lose by agreeing to do these debates and Corbyn everything to gain. In the end, neither emerged victorious but both will feel they lost nothing.

Bertram will speak at Prospect’s election event “Inside the bunker: how to run an election campaign”