Joe Simmonds converted Thomas Waldrom’s last-minute try to cap a dramatic comeback from Exeter, who rallied from 13 points down to edge out Northampton 31-30 at Sandy Park.

The Chiefs were staring at a fourth consecutive Aviva Premiership defeat when they trailed 30-17 with 10 minutes remaining but Don Armand and then Waldrom touched down.

Simmonds kept his cool to add the extras to both tries to seal a nail-biting win and one which took the defending champions above Saracens to the top of the standings.

Unfortunate Northampton could drop to 11th if rejuvenated Worcester defeat rock-bottom London Irish at the Madejski Stadium on Sunday.

Alec Hepburn was Exeter’s other try-scorer. There was also a penalty try award with Gareth Steenson kicking a penalty and a conversion.

Rob Horne, Ben Foden and Harry Mallinder scored Northampton’s tries, all of which Piers Francis converted. Francis (two) and Stephen Myler both added penalties.

Exeter suffered an early setback when Will Chudley left the field for a head injury assessment but the scrum-half missed little as the opening exchanges were scrappy.

Saints fly-half Francis made a particularly poor start with a couple of ill-directed kicks but it was the visitors who took a 12th minute lead when excellent work from Jamie Gibson enabled Horne to finish off a good passing move.

Chudley returned in time to see Exeter respond with a penalty try when Northampton collapsed a driving line-out, with prop Campese Ma’afu yellow-carded.

Francis followed Ma’afu off the field for a HIA with his replacement Myler putting Northampton back in front with a long distance penalty.

Ma’afu and Francis both returned but the game continued to be error-ridden with frequent handling errors and poor ball retention.

After 35 minutes, Exeter took the lead for the first time when a drive from Greg Holmes set up a try for Hepburn, but they were not ahead for long as an excellent break from Luther Burrell allowed Horne to send Foden racing to the line. Francis converted to give his side a 17-14 interval lead.

Within three minutes of the restart, Saints went further ahead when a sharp break from Francis was supported by Horne, who sent Mallinder in under the posts.

Steenson and Francis exchanged penalties before Exeter skipper Steenson was replaced by Simmonds as the hosts chased the game as the final quarter approached.

The substitution did not pay immediate dividends as Francis kicked his second penalty for Saints to lead 30-17 at the end of the third quarter.

With 10 minutes remaining, a break from Olly Woodburn was carried on by Phil Dollman for Armand to cross and set up a grandstand finish.

A late yellow card for Northampton number eight Teimana Harrison ultimately proved costly as Waldrom went in from close range before Simmonds split the posts in the dying moments to rescue an improbable win for Exeter.