Following Celtic's victory - Just how difficult is it to beat Barcelona? - European - Football - The Independent Last night saw an injury-ravaged Celtic side emerge victorious over arguably the best club side on the planet. In terms of the club's rich history, many are lauding Neil Lennon's achievement as second only to the European Cup victory of 1967, but in the cold light of day, when the euphoria has subsided, the question will be posed: Just how difficult are Barcelona to beat? Barcelona's status as one of the world's elite footballing sides has been long established, but it is only since 2008 that the Catalans have commanded an air of invincibility. The beginning of this period of imperious form coincides with the appointment of Pep Guardiola as head coach, and with that, the implementation of the tika-taka style of aesthetically-pleasing football for which they are now known. Guardiola, fresh off the back of an impressive stint as coach of FC Barcelona B, raised eyebrows with his decision to ship the attacking duo of Deco and Ronaldinho out of the club. His brand of tiki-taka football was to revolve around the seemingly telepathic understanding between midfield schemers Xavi Hernandez and Andres Iniesta, both products of the prestigious Barcelona youth academy - La Masia. The emphasis based on recruitment from La Masia, also responsible for the likes of Gerard Pique, Cesc Fabregas and Lionel Messi, coupled with Guardiola's tactical discipline, brought immediate success in the form of a first league title in three seasons and a third European Cup. Two more league titles, two Copa del Rey wins and another Champions League victory later, this Barca team has well and truly established itself as one of the greatest club sides of all time, thereby making Celtic's victory all the more impressive. Last night's result marks the first time Barcelona have been beaten in the Champions League group stages since a shock home defeat to Rubin Kazan in October 2009, thus ending an unbeaten run of 18 fixtures. As well as winning the title in 2009 and 2011, they also reached the semi-final stage in 2010 and 2012, thus illustrating their recent near invincibility in the competition. Despite said form, Barcelona have often struggled when playing in Britain, with the exception of the 2011 Champions League final at Wembley, not managing a victory on this isle since a 2-1 win over Chelsea at Stamford Bridge in February 2006. Gleeful Celtic fans will also point to the fact Barcelona have proven unbeatable in the Spanish league this season, leading the chasing pack on 18 points, and in doing so have equalled the record points tally after ten games in La Liga set by arch rivals Real Madrid in 1997. Clearly, beating Barcelona is no mean feat, and Neil Lennon deserves all the plaudits that will inevitably come his way in the coming days. Although Barca have often fallen short on British shores, last night's events will go down in history as one of Scottish football's all-time greatest achievements.