Another forced change for the French side. Dayna Edwards can't return following his head injury assessment and Walter Desmaison is his permanent replacement.

How often do one side score a penalty then immediately concede another?

Grenoble struggle to get to grips with the hosts' kick-off routine, concede a penalty and Ben Botica slots it through the sticks.

Grenoble are on the board through the metronomic boot of fly-half Jonathan Wisniewski.

That's 28 successive penalties that Wisniewski has kicked now. He's not missed for a month. Impressive stuff.

I make that three assists now for the England scrum-half.

Image source, Getty Images

Grenoble lose prop Dayna Edwards to a head injury assessment, and they lose out at another scrum too.

For the second time already this evening, Harlequins are awarded a free-kick at the set-piece and the French are under pressure.

Even worse for the Top 14 side, centre Nigel Hunt is down with a nasty-looking knee injury.

It's a straightforward kick, in front of the posts about 30m out and, left footed, Ben Botica makes no mistake.

Harlequins take an early lead.

Joe Marler plays a key role as the Grenoble scrum is driven back, conceding a penalty in the process. Ben Botica will go for the posts.

Might it say a lot for the weather conditions that Ben Botica chose to kick rather than run the ball then given the success he's had this season?

Grenoble turn the ball over but can't do anything with it and are rescued after some loose play by being awarded a scrum midway inside their own half.

Harlequins are soon able to relieve any early pressure as Grenoble are penalised inside their hosts' 22. 

Ben Botica kicks across field and Quins enter French territory for the first time.

Referee John Lacey blows his whistle and Grenoble fly-half Jonathan Wisniewski gets us under way.

Harlequins have won seven of their eight home games against French opposition in the Challenge Cup, including the last five. Repeat that form tonight and they're in the final.

Grenoble are bidding to reach their first European final, but are trying to do so in a competition that has been dominated by English sides in recent years.

The teams are out and kick-off is moments away.

It's a soggy evening at The Stoop, with the rain coming down.

Harlequins' home hosted the final of this competition last year as Gloucester beat Edinburgh.

Tonight it's a place in the showpiece that is at stake.

There's five of England's Grand Slam-winning squad in the Quins 23 this evening, but can they 'carry them home' to the final?

England coach Eddie Jones warned last week that a handful of his triumphant squad risk missing out on the summer tour to Australia because they've not played well enough for their clubs.

If you were Eddie, who would you take Down Under or who would you leave behind?

Let us know using #bbcrugby on Twitter.

Harlequins dare not give any cheap penalties away inside their own half then, but, by the same token, Grenoble's defence might be in for a stern test.

Grenoble, who sit 10th in the French Top 14, topped their pool and reached the last four courtesy of a 33-32 victory over Connacht, having trailed 29-16 at one point in the second half.

Tonight's meeting will be the first between these two clubs in European competition.

Image source, BBC Sport

Replacements: Jammes, Barcella, Desmaison, Marie, Vanderglas, Hart, Gengenbacher, Estebanez. 

England prop Joe Marler returns from a two-week ban as Harlequins make five changes.

Former Wales international Adam Jones is also named in the front row, while James Horwill and Luke Wallace return to the pack.

Fly-half Nick Evans is named among the replacements and could return from a broken leg suffered in February.

Image source, BBC Sport

Replacements: Ward, Lambert, Sinckler, Matthews, Clifford, Dickson, Evans, Chisholm. 

But that's enough of my best Judith Chalmers impression - although I wish you'll be here with us throughout the evening.

Before we go any further, let's take a look at tonight's line-ups.

Lyon. France's second city, built around the confluence of the rivers Rhone and Soane.

A modern-day centre for banking, Lyon boasts 2,000 years of history, with a Roman amphitheatre and Latin quarter. It's been an important area for the production and weaving of silk and has now developed a reputation for top French cuisine. 

Image source, Getty Images

It's also a city that both Harlequins and Grenoble would love to visit in three weeks' time for the European Challenge Cup final.

Welcome to our coverage of tonight's semi-final from The Stoop.