The old cliché says, when derby day comes, form goes out the window.

That proved the case at the Swansea.com stadium on Saturday.

Cardiff came into the South Wales derby after four consecutive wins, including a last-minute victory at home against automatic promotion chasers Ipswich last weekend.

Contrastingly, while Cardiff were looking to the play-offs, Swansea were looking over their shoulders and the threat of being drawn into a relegation scrap.

The Bluebirds also had the carrot of a first ever league double over Swansea after a 2-0 win at the Cardiff City stadium in September.

However, Swansea started the game brighter, pressing Cardiff, and looking composed in possession.

Just after quarter of an hour, Harry Darling headed Jamie Paterson’s cross against the bar and, a couple of minutes later, he was involved in the most controversial moment of the first half.

Darling pushed Cardiff striker Yakou Méïté to the ground, but the Ivory Coast international reacted by getting up and appeared to headbutt his opponent in the face.

Had VAR been in operation Cardiff would have surely been down to 10 men, but referee David Webb opted to show both players a yellow card.

For the next few minutes there continued to be some bite to the game with Joe Allen receiving a yellow card for a late challenge on Perry Ng.

It looked as though Swansea would fail to make their dominance count, but after the half hour a ball from fullback Kyle Naughton found Welsh international Liam Cullen on his own at the far post, who produced a cool side foot volley into the far corner.

Cardiff felt Ng had been fouled in the middle, but the goal was given.

The away side were finding it hard to put Swansea under any pressure, with Méïté cutting an increasingly isolated and frustrated figure and the Bluebirds would have felt relieved to enter half time only one goal down and still with eleven on the pitch.

Méïté and David Turnbull were removed at half time by Erol Bulut with last week’s matchwinner Callum O’Dowda and Welsh international Rubin Colwill entering the fray.

However, it was Swansea who would make the first impact in the second half.

Winger Ronald, managed to get inside Ng and the Cardiff defender pulled at his shirt inside the box with Webb pointing to the spot for what appeared to be a soft penalty.

Cullen stepped up to the penalty spot with a chance for his second but contrived to drag his penalty wide with Cardiff goalkeeper Ethan Horvath having dived the wrong way.

Cardiff began to come into the game and looked noticeably better on the ball after the introduction of Wales captain Aaron Ramsey for the final twenty minutes.

Ramsey has been missing since mid-February, and his return to fitness will be a huge boost to Wales manager Rob Page ahead of their play-off against Finland on Thursday.

Swansea have made a habit of falling off in the final twenty minutes of matches recently, but despite the improvement the Bluebirds were unable to find an equaliser.

In fact, with seconds remaining, Swans substitute Jamal Lowe latched onto Ollie Cooper’s pass and beat Nat Phillips for pace before showing great composure to bury the finish and put the nail in the coffin of Cardiff’s dreams of an historic result.

Elsewhere, Newport won 2-0 at Wimbledon to move within two points of the home side and the League Two play-offs, but Wrexham suffered a surprise 0-1 home loss to Tranmere.

Swansea: Rushworth; Naughton (Key 58mins), Darling, Wood, Tymon; Allen (Fulton 72mins), Grimes, Ronald, Paterson (Cooper 72mins), Placheta (Patino 90+1mins); Cullen (Lowe 72mins).

Substitutes not used: Fisher, Yates, Abdulai, Lissah.

Cardiff: Horvath; Ng, Phillips, Goutas, Wilson-Esbrand (Diédhiou 78mins); Wintle, Siopis (Ramsey 72mins), Bowler (Tanner 64mins), Turnbull (Colwill 45mins), Grant; Méïté (O’Dowda 45mins).

Substitutes not used: Turner, Romeo, Ralls, Collins.