Given a sentence in Tagalog language, translate the sentence to English language keeping the meaning of the original sentence intact.

Tagalog sentence: Bago Brighton, class field theory ay isang malalim na kilala lamang sa mga misteryo ng ilang mga (sa Britain, lamang ng isang napaka-ilang nga); matapos Brighton, ito ay isang standard na kasangkapan ng matematika, magagamit sa anumang mga propesyonal.
Before Brighton, class field theory was a recondite mystery known only to a few (in Britain, only a very few indeed); after Brighton, it was a standard tool of mathematics, available to any professional.

Tagalog sentence: Gayunman, na hindi matanggal ang K.
However, that fails to eliminate K.

Tagalog sentence: 4:21 At ang utos na itong mula sa kaniya ay nasa atin, na ang umiibig sa Dios ay dapat umibig sa kaniyang kapatid.

4:21 This commandment we have from him, that he who loves God should also love his brother.