By Andy Silvester Holding a big reception in a genuine greenhouse is a bold strategy, but that’s what Labour Together – the think-tank/campaigning group that has done more to propel Keir Starmer and Starmerism to Downing Street – managed last night, in the Royal Horticultural Society on a day not struggling for humidity. The venue was a late change, admittedly, thanks to the hundreds of late RSVPs. Being close to power is a powerful aphrodisiac for many in Westminster. Rachel Reeves was the star turn, the Chancellor preaching to the converted. It was, it’s fair to say, a friendly audience. The…