What does a cut of tender grouse, a knickerbocker glory and a moreish martini all have in common? They’re all on the menu at 45 Jermyn St, a smart restaurant tucked away in Mayfair which is well worth checking out. The eatery, which is actually within fine food purveyor  Fortnum & Mason, serves up an array of classic and seasonal dishes with grouse season now in full swing. I ventured to dinner on a Friday night and the place had a great buzz. Taking a corner table, I instantly felt at ease with low lighting and some soft jazz music setting the mood. The cosy interiors were designed by...