This afternoon, some 82,000 rugby union fans, and 90,000 football supporters will converge on London for the climax of two great games - the English rugby union championship decider at Twickenham Stadium, and the FA Cup final under Wembley's arch.

It is forecast to be the hottest day of the year so far.

The games play on because we are British, and because sports is in our blood. But, with the country on a state of alert and the terror threat officially at its highest level of critical, those two huge throngs of people will be swelled by security forces with powers to stop and search citizens at gunpoint.

The Wasps v Exeter game at Twickenham, and Arsenal v Spurs 16km away at Wembley, are the rites of spring for Englishmen, women and children.

All players will wear black armbands. And all fans will be subject to stop and search procedures by armed police and military personnel we Brits are simply not accustomed to seeing on our streets.

That the games go ahead is its own statement of defiance against the implicit threat of further indiscriminate terrorism.

Two concerts by the American pop star Ariana Grande scheduled for London on Thursday and Friday were cancelled. Arsenal called off a planned big screening of the Cup final at the Emirates Stadium on police advice.

And whoever wins the final will not go ahead with the familiar open-top bus parade tomorrow.

These are not normal times, and following last Monday's inhumane slaughter of innocents in Manchester, there was no victorious celebration for Manchester United players after their Europa League win over Dutch side Ajax Amsterdam in the Friends Arena in Stockholm on Wednesday night either.

But that game played on, 48 hours after the Manchester Arena atrocity. It was only a game, though it was written up as the same spirit of defiance seen in its broader concept by people of all faiths in Manchester's Albert Square.

Can we have normal sport in an abnormal society?

I remember that conundrum being phrased in exactly the opposite way in Northern Ireland during the deadly decades of the Irish Republican Army. I vividly remember sitting between two fathers whose sons played in the same team during a final of the Carnbane children's league in Newry, an Ulster town near the border with the Republic of Ireland.

It was the 1970s, and those fathers were on opposite sides of the sectarian divide.

That day, they literally laid down arms to cheers their boys to a trophy. Afterwards, they returned to the violence.

"There can be no normal sport in an abnormal society," a government minister said.

But what is the alternative? From the 1972 Munich Olympics, which continued after the Black September Palestinian murders of 11 Israeli athletes and officials, through the Mumbai bombings and the targeting of the Stade de France during the Paris attacks in 2015, the choice has been abandon sporting events, or play up and play on.

This week's horror in Manchester was at a Grande concert. Its targets were youngsters having a night out.

Sport, too, is about bringing together people for enjoyment. "Football is the most important, of the least important things in life," said Carlo Ancelotti when he was the coach at Real Madrid.

The Italian is one of life's winners. He has changed his colours as often as some people change coats. He won as a player, then as a coach, with AC Milan, Juventus, Chelsea, Paris St-Germain, Real and Bayern Munich.

Another Italian, Antonio Conte, has followed him to Chelsea and is attempting today to emulate his league and cup double in charge of the Blues in the 2009-10 season.

Football doesn't ask to see a man's passport. Anyone can share the dressing room with anyone.

Most teams in the richest league, the English Premier, have Muslims side by side with Christians. Just like the Carnbane youth league, what matters is how you play the game.

It just so happens that Riyad Mahrez and N'Golo Kante, the best EPL players of the last two seasons, are Muslim.

We shouldn't even have to ask, any more than we now accept that the colour of a man's skin is irrelevant to the skills that make him part of a team. But there are Muslims in most of the great teams - Yaya Toure at Manchester City, Paul Pogba at United, Mesut Ozil at Arsenal, Franck Ribery at Bayern Munich, Karim Benzema at Real Madrid... the list goes on.

In fact, the bigger divide in the world's most popular sport is money. Pogba cost United £89 million (S$159 million) , a record fee that will very soon be exceeded. That sum is double the cost of the entire Ajax line-up.

"You can't score with a bag of money," is how Johan Cruyff, the club's finest player of them all, described the Ajax philosophy.

Ajax attempt, still, to breed rather than to buy success. Their team were the youngest to take the field in a European final. Okay, they lost to a deflected goal from a Pogba shot, and an acrobatic strike by Henrikh Mkhitaryan, the first Armenian to play in England.

Today, Arsenal and Chelsea will field a league of nations. Tomorrow in Monte Carlo there will be a race around Monaco which sets the template for street car racing.

Singapore converted that very special formula into the spectacle of a night race, when the heat is less intimidating. Think about that when you see pictures of police and soldiers, armed to the teeth and wearing heavy body armour, at Twickenham and Wembley today.

Britain's capital is keeping tradition alive. Barring something unconscionable, the games are on because sport cannot - and will not - surrender to intimidation.