Two tries apiece from second-row John Brear and fleet-footed winger Garrett Bell, together with the steady boot of Tom Jewitt enabled Leamington to win this hard-fought derby, played in testing conditions.
Despite the wet surface and biting cold, both outfits worked hard to put on a very entertaining match to warm a large derby crowd.
Leamington broke the deadlock following a clever kick upfield by Jewitt which was chased down by full-back Rich McKowen to put the visitors on the back foot. The Leamington pack were quick to react and increased the pressure on the visitors with a surge to the line, allowing Brear to get the decisive touchdown.
From wide out, Jewitt coolly slotted over the conversion.
The lead was short-lived as Southam took advantage of a home yellow card following a spot of handbags to score through winger Nathan Hooker. Will Grindal converted the try and then added a penalty just before the interval, awarded for not rolling away, to give his side a slender three-point advantage at the break.
The home side began the second period in a positive manner after a kick out by scrum-half, Sam Nunn was chased down by the willing McKowen to put Southam under the cosh.
Having gained a penalty, Leamington opted for a scrum and were only denied a try by some last-ditch defending.
A penalty relieved the pressure and from the resulting lineout Harry Hewson put up a high kick which was collected on the run by Will Clarke who then won the foot race to score under the posts.
Grindal added the conversion to open up a useful ten-point lead.
McKowen provided the catalyst for the Leamington response with a break up the wing. From the resulting scrum, Smith picked and ran at the Southam defence. Dan Barber kept the move flowing with a determined drive and when Brear appeared in support, there was no stopping him claiming his second try of the afternoon.
The Leamington momentum continued and with Kenny Kwok now on as replacement, his first touch of the ball proved crucial.
With little room to manoeuvre, he managed to outwit several defenders with a direct sprint down his wing before offloading inside. The Leamington backline were all alert and when Jewitt sent out a sublimely flighted pass to Bell, the winger powered through to score.
Jewitt slotted over the conversion to put his side 19-17 up.
The hosts increased their lead courtesy of a Jewitt penalty and took advantage of a yellow card for Southam second-row Rich Lloyd to add a bonus-point try through Bell.
The winger read his lines beautifully, taking possession from Jim Robertson at pace and crashing over between the posts. Jewitt added the extras.
Southam ralled in the closing stages with some good phases and go-forward.
Lewis Dodds was put into touch five metres out but Southam ripped the ball from the lineout maul and prop Charlie Gilkes showed slick hands to feed hooker Elliot Cook into space and he scored in the corner.