Father and son Kevan and Alan Hall sit in and analyse meetings for clients because bad meetings are a huge waste of time and resources in today's business world. What's a bad meeting? Well, if you don't need to be there, you're already into the realm of badness and if you're in back-to-back meetings from nine to five, when are you supposed to get your work done? Kevan and Alan have written a book called Kill Bad Meetings and they agreed to meet with Richard Curran – remotely from a BBC studio – to discuss the book and share tales of bad, bad meetings.

"A lot of people are accepting invitations to meetings when they don't know what the agenda is and what their role is, so they're showing up saying, whatever you choose to fill my day with is more important than my time, which seems crazy."

The rise of the meeting in business culture really is extraordinary. Kevan and Alan had plenty of examples of bad business meeting practices, including one executive who was flown from China to Singapore, shown a video and then flown home again. For Kevan, relevance is really important in a meeting. A good meeting is one where "everyone's engaged and everyone needs to be involved".

"Fairly consistently, between ten and twenty percent of people shouldn't even be in the room. So step one is getting rid of those people."

Richard wondered if unnecessary meetings were costing companies money, Definitely, was the answer. Kevan and Alan have asked around 4,000 people who've come through their training programmes who reasonably consistently told them that they spend two days a week in meetings, and half of that time is irrelevant. And these tend to be the most expensive employees – the managers, the professional people. So the costs of bad meetings can really add up:

"It's probably costing €20,000 per year for every professional employee you have."

When you scale that figure up for bigger companies, you can be talking about millions of euro a year. But it's a hidden cost because it's split across everybody's time and everybody's travel budget.

"I'm surprised that big companies don't have someone actively managing this."

What, Richard asked, is the alternative to these unnecessary meetings? There isn't a clear answer. Kevan says just cancel them. Alan has a more nuanced view: although some meetings may not need to happen at all, some employees see them as a chance to make a good impression, something which can't happen if the meeting doesn't go ahead, or if they're not in the room.

You can hear the full meeting – sorry, conversation – with Kevan and Alan Hall, as well as the rest of  The Business here.