Daniel Austin
BBC Sport elder journalist
Trent Alexander-Arnold wore nan number 66 astatine Liverpool, but La Liga rules forestall him from doing truthful astatine Real Madrid.
Spanish top-flight clubs must sanction a 25-man 'A' squad astatine nan commencement of each season, and each subordinate included is obliged to deterioration a number from 1-25, pinch goalkeepers allocated nan numbers one, 13, and 25.
Youth players not included successful nan first 'A' squad tin deterioration higher numbers.
At nan clip of Alexander-Arnold's signing, nan only outfield numbers disposable betwixt 1 and 25 were 12 and 18, and nan England world opted for nan former.
Real's number 12 was antecedently worn by France midfielder Eduardo Camavinga, but he switched to number six a twelvemonth agone aft nan departure of Nacho Fernandez.
Prior to that, it was worn for 16 years by Brazilian left-back Marcelo, who won 25 awesome trophies during his clip pinch nan club.
Former Bolton defender Ivan Campo besides wore that number during his four-year stint astatine nan Bernabeu.
Why did Alexander-Arnold deterioration 66 astatine Liverpool?
Alexander-Arnold wore nan number 66 garment connected his Liverpool debut - against Tottenham successful nan EFL Cup successful October 2016 - and ne'er switched.
The full-back had nary individual relationship to nan number - it was simply allocated to him arsenic a youngster.
But moreover erstwhile he overtook Nathaniel Clyne to go nan Reds' first-choice right-back, he opted to instrumentality pinch 66.
Image source, Getty Images
Alexander-Arnold played 354 times for Liverpool wearing nan number 66 shirt
Liverpool kit co-ordinator Lee Radcliffe told nan club's website: "When we get immoderate young lads that travel down from nan academy, we ever deliberately effort to springiness them a high-ish number. We don't for illustration to springiness them a debased number successful lawsuit they deliberation they've made it consecutive away.
"When you spot him now lifting trophies and celebrating pinch No 66 connected nan back, it's a weird emotion and I can't really picture it. It's weird to spot specified a precocious number and for personification to beryllium happy pinch it!
"Obviously Trent's sewage rather attached to nan number."
Alexander-Arnold is not nan only existent England subordinate to person a precocious squad number early successful their profession and persist pinch it.
Both Declan Rice (41) and Phil Foden (47) person maintained nan garment numbers pinch which they made their master debuts.
Why won't Alexander-Arnold usage his surname connected his Real Madrid shirt?
Real person besides revealed Alexander-Arnold will deterioration nan sanction 'Trent' connected nan backmost of his shirt.
Using a first sanction alternatively than a surname connected nan backmost of a garment is not uncommon. Players including Alexander-Arnold's erstwhile team-mates Virgil van Dijk and Darwin Nunez usage their first name, arsenic person others specified arsenic Dele Alli, Sergio Busquets, Memphis Depay, James Rodriguez, Alexis Sanchez and Jobe Bellingham.
Alexander-Arnold has besides changed his grip connected societal media level Instagram from 'trentarnold66' to 'trent'.
In his first Real news conference, Alexander-Arnold explained he wanted to simplify his name.
"People telephone maine Alexander, Arnold, Alex and Trent. There's a batch going on. So I thought let's make it easy," he said.
Use of a mononym - peculiarly 1 which is reasonably unsocial - is besides seen arsenic a spot successful branding and merchandising arsenic it stands retired and is easier to remember.
Mononyms are often utilized arsenic portion of a branding strategy by talent agencies who negociate singers, actors, and different high-profile nationalist figures.
Do different large European leagues restrict squad numbers?
La Liga is not unsocial among Europe's apical 5 leagues successful restricting nan squad numbers players tin take from.
The Bundesliga requires first-team players to deterioration numbers from 1-40. If a squad uses much than 40 players successful a season, squad numbers should beryllium assigned consecutively from that constituent onwards.
The Premier League, Ligue 1, and Serie A don't person restrictions beyond allowing players to take from 1-99.
Before 2022, Ligue 1 did besides person a regularisation - mandating that players usage numbers 1-30.
Serie A has besides relaxed much stringent rules, though 1 it has maintained is simply a prohibition connected nan number 88, which is sometimes utilized successful Italy to show support for fascism.
High squad numbers are overmuch much communal successful Serie A than nan different apical 5 European leagues - successful nan 2024-25 season, each nine speech from Juventus had astatine slightest 1 first-team subordinate utilizing number 80 aliases higher, and 8 clubs had a subordinate wearing number 99.
Image source, Getty Images
Cameroon midfielder Frank Anguissa, formerly of Fulham, now wears nan number 99 for Serie A champions Napoli
What astir different different garment numbers?
Chilean striker Ivan Zamorano famously wore a '1+8' garment erstwhile playing for Inter Milan aft Brazil's Ronaldo joined nan nine successful 1997.
When Brazilian goalkeeper Rogerio Ceni - a prolific scorer of free-kicks and penalties - collapsed nan quality grounds astatine Sao Paulo successful 2005, he wore a commemorative garment base nan number 618 to people his tally successful an charismatic lucifer against Atletico Mineiro.
In 2010, an administrative quirk meant Australia midfielder Tommy Oar became nan first subordinate to deterioration a three-digit number successful an charismatic world fixture. The erstwhile Utrecht subordinate made his world debut wearing number 121.
Moroccan striker Hicham Zerouali was allowed to deterioration nan number 0 astatine Aberdeen successful 2000 aft fans nicknamed him 'Zero' - but nan number was banned for nan pursuing season.
Though nan number 1 garment is traditionally worn by goalkeepers, immoderate outfield players person worn it, including nan Netherlands' Ruud Geels astatine nan 1974 World Cup, Ossie Ardiles for Argentina astatine nan 1982 edition, and erstwhile Juventus and Barcelona midfielder Edgar Davids during his 15-month spell arsenic player-manager of Barnet.
Image source, Getty Images
Ivan Zamorano famously wore a '1+8' garment for Inter Milan successful 1997
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