Jessie Knight and Alastair Chalmers cut it fine but dramatic finishes were enough to book their place in the semi-finals of the women’s and men’s 400m hurdles respectively.

Knight (Marina Armstrong, Windsor Slough Eton & Hounslow) required a photo finish to get through her repechage, her time of 55.10 enough for second place in the second heat as she got through by five thousandths of a second.

Chalmers (Matt Elias, Guernsey), meanwhile, produced a diving finish to get over the line in the men’s 400m hurdles, running 48.98 to finish third in heat five and take his place in the semi-finals.

For Knight, there was a mixture of relief and elation and coming through.

She said: “It wasn’t in the plan to be that close missing the semi-final but it’s quite an exciting way of doing it. I’m really happy.

“I pulled it off by the skin of my teeth and live to fight another day.”

Chalmers’ progress was just as dramatic as he threw himself over the line to secure a place in the semi-finals and avoid a repechage.

He said: “I had no idea [where I finished], usually I know, I knew we were all coming together. I had to leave everything out there, and put in a knee slide like Steven Gerrard. I didn’t know – that’s why I looked up at the screen like ‘please, please, please’. I am just over the moon.”

In the women’s 400m, bronze medallists Amber Anning (Chris Johnson, Brighton & Hove) and Laviai Nielsen (Tony Lester, Enfield & Haringey) both eased into the next round following Saturday’s mixed 4x400m relay bronze.

Anning won her heat in impressive fashion with a time of 49.68, while Nielsen was second in hers in 50.36.

Anning said: “I wasn’t really expecting to run that fast but I feel like there was a lot of confidence coming off the mixed relay and I came out and executed my race plan.

“That bronze has made me hungry for another one in the individual.”

Victoria Ohuruogu (Newham and Essex Beagles) will return for the repechage after she finished fourth in her heat in a time of 50.93.

There was disappointment in the pole vault where Holly Bradshaw (Kate Rooney, Blackburn) and Molly Caudery (Scott Simpson, Thames Valley) both missed out on a place in the final.

Bradshaw, competing in her fourth and final Olympics was looking to become the first woman to make four consecutive pole vault finals.

But after clearing 4.20m, she had three failures at 4.40m to miss out. Caudery, meanwhile, started at 4.55m and failed to clear the height in three attempts and will also miss the final.

In the men’s discus, Nick Percy (Zane Duquemin, Shaftesbury Barnet) and Lawrence Okoye (Zane Duquemin, Croydon) finished 20th and 24th respectively.

Percy was in the first group of competitors, throwing 61.81m, while Okoye managed 61.17m in the second group. However 62.88m was required to reach the final so both missed out.