There is a mosque in the city of London where the Friday prayer is held twice on the same day with two sermons due to disputes between the congregants. What is the ruling for this?

Allah the Almighty has forbidden Muslims from arguing with each other. He informed us that such behavior breeds widespread corruption on earth and that such differences are the means for failure and subjugation by other nations. He commanded us to rectify relations between disputants and to remind them of His favor when He converted enmity into brotherhood. He said, And hold fast, all together, by the Rope which Allah (stretches out for you) and be not divided among yourselves; and remember with gratitude Allah's favor upon you; For ye were enemies and He joined your hearts with love, so that by His Grace ye became brethren.[Al-Imran: 103]

So fear Allah, and keep straight the relations between yourselves: Obey Allah and His Messenger if ye do believe.[Al-Anfal: 1]

And obey Allah and His Messenger; And fall into no disputes lest ye lose heart and your power depart.[Al-Anfal: 46]

The Unbelievers are protectors of one another; Unless ye do this. (Protect each other)

there would be tumult and oppression on earth, and great mischief.[Al-Anfal: 73]

The believers are but a single brotherhood: so make peace and reconciliation between your two (contending) brothers; And fear Allah, that ye may receive mercy.[Al-Hujurat: 10]

It is known in Islamic law that the reason for holding Friday prayer is to manifest the ideal of solidarity and unity of the [Muslim] word. For this reason, the majority of scholars have stipulated that, for its validity, Friday prayer must not be preceded or be held simultaneously with another in the same town except if it is difficult to assemble the congregants in one location. Holding more than one ceremony is subject to necessity. It is invalid to hold more than one Friday prayer in the same mosque and the valid prayer is that which is led by the appointed imam of the mosque.

The ruling

Muslims must resolve this dispute and hold a single Friday prayer since this establishes unity between them.

It is impermissible in Islamic law to hold Friday prayer in the same mosque twice. The valid prayer is that which is led by the appointed imam of the mosque, whether it is the first or second. The other prayer is therefore invalid because it is considered arrogating the prerogative of the imam. Those in charge of the affairs of Muslims must ascertain that only one Friday prayer is held in a single mosque and is led by the appointed imam. The reason for this is to unite Muslims and eliminate any rifts between them.
May Allah grant Muslims success to what pleases Him.
Allah the Almighty knows best.