By Saskia Rowlands Visitors who fancy the soup at the King’s Highgrove country pile will need plenty of bread to pay for it. A bowl of Brown Windsor at the cafe is £12 – up 60% from £7.50. And the cheapest salad costs a princely £17.95 this year, up from £10.50 previously. Around 35,000 people a year tour the gardens at Highgrove, near Tetbury, Glos, which are open from April to September. They tuck into “seasonal culinary delights” prepared by estate chefs in the Orchard dining room, according to the website. But its £13.50 salmon quiches and £9.50 sarnies have been replaced by chicken breast…