Speedy winger Lennon - one of three changes made by Martin Jol - was on the spot to convert when Jermain Defoe's cross evaded Jermaine Jenas after 65 minutes. Lennon controlled, shifted onto his left foot and drilled into the corner.
We had a number of breakaway chances in the first half that didn't come to much but we showed a clinical edge after 77 minutes as Keane bagged the crucial second goal and a much-needed fifth away win of the Premiership campaign.
The pressure was on with Arsenal, Blackburn and Bolton all winning before we kicked-off but the lads delivered when it mattered.
Defoe in for Mido and Kelly for Paul Stalteri were other two changes with Mido, Stalteri and Teemu Tainio all on the bench.
For Kelly, his inclusion was a timely reward for his displays in the reserve side where he has scored two goals in his last two outings. He showed good early poise in setting Defoe off on a run towards goal, but Maik Taylor was first to a slightly over hit through ball. Taylor was then alert in fielding a low driven free-kick from Michael Carrick.
The was a momentary scare on seven minutes when Jenas was dispossessed in a robust fashion by Nicky Butt, which allowed former Brentford man DJ Campbell a dart on goal. After a couple of twists and turns, he ran out of space and Paul Robinson was not tested.
Two minutes later Emile Heskey powered past Ledley King to the right of the area and drilled across goal - only Michael Dawson deflecting the ball slightly out of the path of Campbell prevented what would have been a probable opener.
Birmingham were in their stride and applying the early pressure. It was Steve Bruce's side showing more purpose as the clock ticked towards the half hour mark. However, a sprint from Jenas looked like it might just create an opening before his pass located Defoe in an offside position.
Heskey embarked on a similar dash to Jenas at the other, but went down a little too easily in the penalty area under pressure from a retreating King.
It was not a fluent or flowing half from our point of view, passes were going astray and there was a lack of cohesion in the build-up. The home side will have been happier with their work in the first 45 minutes, but it was so nearly undone when Jenas sped down the right and crossed low into the path of Keane in front of goal. It took a brave and excellent block by Mario Melchiot to prevent his side falling behind.
A flick by Keane after a scrappy first eighty minutes to the second period set Defoe scurrying away before unleashing a rising shot that Taylor did well to tip over. From the resulting corner, Dawson took aim towards opening his account, but his drive was deflected away in front goal by Butt with what looked like his arm.
Mikael Forssell was introduced in place of the troublesome Heskey just before the hour mark, but the next attacking player to make a big impression was Lennon. It was Defoe who showed the battling qualities to shake off both Melchiot and Cunningham to the left of the Birmingham area and managed to squirt the ball into the box where Lennon was waiting to pounce.
After taking a touch or two, the speedy winger steered the ball low past Taylor and into the bottom right hand corner of the net for his first Spurs goal. Cue joy from the travelling thousands who braved the freezing cold.
Birmingham responded but kept coming up against the towering presence of Dawson.
On 77 minutes came the sweetest of moves that led to the always crucial second being netted by Keane. Lennon and Kelly between them squeezed the ball to Carrick near the half way line and the England man dispatched a precision pass down the flank which was seized on by Jenas.
Jenas once again showed his speed but also a brilliant low pass across the six yard box which presented Keane with an open invitation to score at the far post which he was not about to refuse.
Aaron Lennon's first goal for us and another from Robbie Keane secured a vital victory at St Andrews on Saturday.