'Should I wear the rubies, the emeralds or the diamonds?' is a question Jenny Glassborow has got used to answering over the past 20 years. And one she looks forward to getting asked.

Jenny works in Safe Custody, a service offered by Coutts whereby valuable possessions are stored for clients - possessions that often include their jewels.

Joining Coutts straight out of school 26 years ago, the last 24 years of Jenny's career have been spent specialising in Safe Custody, and supervising the 'Strong Room', a large room where the valuables are stored, located two heavily secured floors beneath 440 Strand.

It's a room clients have used for hundreds of years with shelf after shelf of trunks, suitcases and boxes dating back to world war times and beyond. Owners have included Winston Churchill and William Gladstone, along with more current clients many of who are prominent figures from the worlds of music, media, sport and business.

Jenny knows each and every box and trunk like the back of her hand. Point one out and she'll know the owner, their background and the date it was brought in. But chances are she won't know what's inside.

Many of the boxes were stored before Jenny joined Coutts, a time when neither she nor her predecessors were required to look inside them before they were deposited (this changed after 9/11). The only time she sees the contents of those are when clients come in to visit and open their box… which is how she's become a bit of jewellery connoisseur.

"Because the client's granddaughter wasn't able to come with him, I had to try on the tiaras and help him choose which one would be best for her wedding day."

"We get so many clients coming in to see their valuable possessions, especially the elderly who drop in quite regularly," she smiles. "For me, it means going down to the Strong Room, finding their box, and then bringing it into a special room where they can look through their things."

Often, clients sit there for long periods, trying on their jewels and reminiscing with Jenny about where they came from and when they received them. Others visit to collect specific pieces for high profile events or weddings, and then return them the next day. "Like one client who was going to the Windsor ball," Jenny remembers.

"I got her box, then went into the special room to see her, and she suddenly took off her top, pulled on another one and said 'Jenny, this is the colour of my dress. Now should I wear the rubies, the emeralds or the diamonds?'

"It's the nicest part of my job, the really personal side of Coutts. You get to know clients so well, and they ask for your help and opinion on things. It's fantastic, I love it."

Another client's granddaughter was getting married recently, and made an appointment with Jenny to check his box so that he could pick out one of the family's tiaras for her.

"But because she couldn't come with him, I had to try them on and help him choose. The next time I saw that tiara was when the granddaughter came in with her hairdresser and, in the room, came up with a hairstyle for the bride complete with tiara on. Then it went back in the box until the big day when it was insured," she explains.

"If we can't locate the owner, the law states we must keep their belongings for 100 years before we can do anything with it."

Alongside jewellery, there are many more valuables in the Strong Room which holds over 20,000 items. There could be anything from silverware, jewellery, paintings or documents such as clients' wills inside the trunks – things they want kept safe in case they are ever burgled. "I do know that we have some Picasso's and modern art, but as to the overall value down there, it's unknown," she admits.

Before 1996, Jenny and her team were still using ledgers to track deposits and log new ones. But besides the recent IT improvement, very little else has changed in Safe Custody over the years. "When people come to see us, they say it's like a step back in time," laughs Jenny.

And with good reason. Many of the boxes date back to the 1800s and beyond. What happens to those? "Sometimes clients leave the bank for whatever reason and their accounts are closed but they forget their box. If we can't track them down to return it, then we get archivist Tracey Earl to look through the Who's Who books to investigate other connections to them.

"If we can't locate anyone that way, the law states we must keep the box for 100 years before we can do anything with them. At the moment, Tracey is looking into quite a few items. If people are not found, the contents will go into our archive."

The Safe Custody service is more in demand than ever these days. In fact, the whole Strong Room had to be expanded in 2000 to create more space for new deposits. It was a huge operation that proved worthwhile, and Jenny's confident there won't be any space shortages for the foreseeable future.

She's also confident about the security surrounding the Strong Room against theft and robberies. "We've been around 300 years and nothing's happened yet," she smiles. "Our clients continue to feel that we're the safest place to store their valuables. And, being honest, I couldn't agree more."

To use the safe custody service at Coutts, contact Jenny Glassborow on 020 7753 1000. The cost is £50 (inc VAT) a year for a small box and £110 for a big one

By Barbara Walshe