Watching Barcelona at the top of their game is always a special treat to savour – and when the world’s best player Lionel Messi is in the groove we are talking fantasy football.

Still only 24, Catalonia’s adopted Argentinian is not only the undisputed No.1 player on the planet, he is strengthening his claim to be the greatest of all time with each passing year.

The way Barca destroyed Bayer Leverkusen in the Champions League tonight with a breathtaking 7-1 demolition that completed a 10-2 aggregate win was an awesome display, crowned by Messi at his mesmeric best. The maestro’s five goals were a record for the competition and took his tally to 14 in his last five outings for club and country.

Last May, when we saw the Catalans raise the bar with an imperious victory over Manchester United in the Final, a virtuoso performance by the pint-sized magician inspired me to write “still only 23, Messi is the already arguably the greatest player the world has ever seen.” The truth is he is still several years shot of the age when footballers are traditionally considered to be at their peak.

Messi the undisputed No.1 is staking claim as the best ever – he even makes great commercials . . .

No wonder Franz Beckenbauer predicts Messi can reinforce Barca’s status as the best team arguably of any generation by becoming the first side to retain the trophy since the ­ introduction of the Champions League format.

Germany’s World Cup winning skipper, who lifted the European Cup three times with Bayern Munich in the mid-1970s, said: “Messi is a genius. He has ­everything. When I watch him, I see a player who is very, very, skilful, very clever – and his left foot is like Diego ­Maradona’s.

“The difference is Messi is also like Bobby Charlton. He is a nice man, he’s a gentleman. You will never hear from him telling you bad things about this or that.”

‘Der Kaiser” – whose beloved Bayern Munich side hope to join Barca in the quarter-finals – concedes: ­“Barcelona are the best team in the world. Almost perfect.

“If you see them play, they are fantastic. Of course they are not unbeatable, we have seen that, but in general they are not only the best team but one of the most spectacular teams in the world. I believe they are right up there with the great teams of the past, Real Madrid, Johan Cruyff’s Ajax and my Bayern.”

Why on earth coach Pep Guardiola would even consider leaving Barcelona, who have the opportunity to dominate the game for years to come, is beyond me.