in series 4. No more dances were added until series 7, in week 11, when couples performed either a Charleston (which winner Chris Hollins chose to perform again in the final) or a Rock N' Roll routine. The final also featured a head-to-head Lindyhop. Of these dances, only the Charleston was retained for subsequent series, although elements of the Lindyhop have often featured in Showdances. Series 8 introduced the Swing-a-thon, where all remaining couples danced Swing simultaneously and were voted off the dancefloor one by one by the judges until only one couple remained. This returned in series 9 and 11. The tenth series featured a "Dance Fusion", in which the couples attempted to perform two dances consecutively in one routine. The twelfth series introduced the Waltz-a-thon, which used the same manner as the Swing-a-thon: all remaining couples danced the Waltz on the dance floor at the same time. Afterwards, the results were revealed by the judges. The thirteenth series introduced a Quickstep-a-thon, in which all seven remaining couples simultaneously danced the Quickstep. The judges then ranked them from one to seven and gave points accordingly. The fourteenth series saw the Cha-Cha-Challenge introduced, in which all six remaining couples simultaneously danced the Cha-Cha-Cha. The judges then ranked them from one to six and gave points accordingly. The fifteenth series saw the Paso Doble-thon introduced, in which all seven remaining couples simultaneously performed a Paso Doble. The judges then ranked them one to seven and gave points accordingly. The sixteenth series saw the Lindy-Hop-athon introduced, in which all seven remaining couples simultaneously performed the Lindy Hop. The judges then ranked them from one to seven and gave points accordingly. The sixteenth series introduced Contemporary, Jazz, and Street/Commercial dances as part of a "couples' choice" category. A Showdance (Freestyle) has always been performed in the series final as a last chance for couples to impress the public. From series 2 to 7, the Showdance was not scored by the judges. From series 8 to series 18, and again in series 20, the Showdance was performed as each couple's second dance in the final. Prior to series 10, the dances performed in the early weeks were switched between one Ballroom and one Latin, and were divided as evenly as possible depending on the number of contestants left. As the competition progressed further, this system was abandoned and many styles, not just two, could