National Gallery launches new learning centre, the first bicentenary capital project to open to the public / Rubens masterpiece in National Gallery may not be legitimate, fresh evidence claims / National Gallery pulls all-nighter for Van Gogh: Poets and Lovers final weekend / National Gallery brings rarely seen drawings out of the vault for exhibition / National Gallery bans liquid after attacks on artwork / National Gallery demolition workers find funder's secret critical note / National Gallery finds 'unhinged' note hidden in hollow concrete column for decades / Stunned National Gallery workers find prophetic letter from decades ago hidden in column / Builders renovating National Gallery find funder's letter commending demolition / National Gallery lends famous art for first time