Another capital city, another outrage. Last time out, in December, it was the Hungarian capital, Budapest: where some of Chelsea's travelling support were heard to sing an antisemitic chant inside the Groupama Arena; and displayed banners bearing Nazi insignia outside.

This time the Czech capital, Prague: where a group of fans filmed themselves singing an Islamophobic song about the former Chelsea man Mohamed Salah.

And you don't have to cast the memory back too far to recall the night in the French capital, Paris: where some of Chelsea's travelling support pushed a black man off a train, and others chanted "we're racist and that's the way we like it".

Chelsea has a serious problem with racism among a section of its support. And it is no fleeting issue.

Those headline incidents are just the first three that come to mind, but there are any number of others that could be mentioned.

From the routine singing of songs celebrating Nazi death camps (both historic and current – British Transport Police are handling a number of cases from this season), to the alleged racial abuse of Raheem Sterling – it just goes on and on.

This latest incident was different, in that it was recorded by the fans themselves, and posted online.

People so brazen, or so stupid, that they are desperate to share the evidence of their vile discriminatory behaviour with the world.

Well it seems they've got what they wanted: their gurning mugshots on the back pages of at least two national newspapers (which should make for an interesting chat when they return to work on Monday); and Chelsea's name dragged through the mire again.

And, because of that, the club was able to snap into action to immediately ban some of these morons on tour: three of six were refused entry to the Eden Arena on the night; all of them will be sought out, in pursuit of further action.

This is not a new problem at Chelsea: the club was infamously infiltrated by the far right during the 1970s and 1980s; with Nazis selling National Front News and The Bulldog magazine at Stamford Bridge.

Those days were supposed to have passed. But some of the fans involved back then are certainly still full-time fixtures within the Blues' support.

And there is a feeling, now, that a similar sort of infiltration has taken place in recent years.

Young men with far right views pepper the club's social media.

They share tales of their escapades when attending games; but also re-tweets of the fascist political party Britain First, the (now deleted) Twitter feed of far right agitator Tommy Robinson, or other extremist spokesmen from the UK and abroad.

Call out the racism, and you'll hear from them: as I have, repeatedly over the last couple of years since their behaviour has become more and more objectionable.

They strike back with abuse, threats, yet more racism, and a torrent of whataboutery.

A quick look down the accounts associated with that Prague video reveals a list of names that includes regular senders of threatening or abusive bile to my mobile handset.

They all seem to believe that there are no moral or legal constraints on their behaviour; that they are above the law, wherever they live, or in whatever city they have just arrived.

So why Chelsea? Maybe it's an easy target on which to pin their extremism, given the history of the club?

Certainly a large number of those most forthright in their far right beliefs quote on their social media profiles locations in the home counties not previously known as being hotbeds of Chelsea support.

The Shed End at Stamford Bridge in 1984.Eurosport

As the NF back then drew like-minded people from far and wide; are some shady, unseen recruiters now doing much the same?

Chelsea has been at the forefront of tackling this curse: it speaks determinedly against each episode, and campaigns widely.

"Chelsea FC finds all forms of discriminatory behaviour abhorrent and where there is clear evidence of Chelsea season ticket holders or members involved in such behaviour, we will take the strongest possible action against them," said the club on Wednesday evening.

"Such individuals are an embarrassment to the vast majority of Chelsea supporters who won’t tolerate them in their club.

If there is any minor criticism of their stance, it is that talk has come easier than actions.

Why is nobody employed within the club to monitor the social media activity of its most extreme hangers-on?

And why is there so little evidence of people being banned for these recurring events – several supporters have confided that they would like to see people named, shamed and pictured in the match programme.

Having said all that, in Prague the action was impressively swift, and decisive.

Six more scumbags that right-thinking fans will hopefully never have to share an away section with again.

It's a miserable, depressing way to filter out the filth; but it does, at least, appear to be slowly having the right effect.

Dan Levene @danlevene