By Adam Dutton & Sam Elliott-Gibbs A woman who picked up a brooch for £20 at a local market says she can’t believe it’s about to go to auction and is expected to fetch around £15,000. Unsuspecting Flora Steel purchased the silver badge 35 years ago not realising it was a “historically significant” piece of jewellery dating back to the 19th Century. She contacted auctioneers after noticing the design was similar to one which appeared on the BBC hit series Antiques Roadshow \- and later sold for £31,000. Flora was left gobsmacked when experts revealed her brooch was also an original by the great…