Infinity routes internal to the BT network Winchester->Sheffield->Ilford; and to reach Xilo or Uni in Sheffield it appears to route Winchester->Sheffield->Ilford->Sheffield.
They've removed the names of many of the BT internal routers, so it's harder to be sure that is what is happening; the intermediate ones with the increased hop time used to be explicitly named with a 'shef' in them. I'd be interested if anyone had a different interpretation of this tracert.
Tracing route to sheffield.ac.uk [143.167.2.101]
over a maximum of 30 hops:
1 <1 ms <1 ms <1 ms 192.168.1.254
<<< Winchester
2 15 ms 15 ms 14 ms 217.32.147.100
<<< includes around 8ms interleaving
3 15 ms 15 ms 15 ms 217.32.147.142
4 19 ms 19 ms 19 ms 212.140.206.82
<<< +4ms, for hop from south to north ?
5 19 ms 18 ms 18 ms 217.41.169.251
6 19 ms 19 ms 19 ms 217.41.169.109
7 18 ms 19 ms 18 ms 109.159.251.239
8 28 ms 27 ms 27 ms core1-te0-12-0-6.ilford.ukcore.bt.net [109.159.251.133]
<<< +4 for hop from north to south, plus slow response to ping
9 29 ms 31 ms 35 ms peer3te-0-3-1-0.telehouse.ukcore.bt.net [62.172.102.9]
10 24 ms 26 ms 24 ms 195.99.125.18
11 26 ms 26 ms 25 ms ae0.lond-sbr4.ja.net [146.97.35.109]
12 26 ms 26 ms 27 ms ae13.lond-sbr1.ja.net [146.97.33.133]
13 29 ms 29 ms 29 ms as3.leed-sbr1.ja.net [146.97.33.97]
<<< +3 for hop from south to north
14 32 ms 33 ms 31 ms YHMAN-L1.site.ja.net [146.97.42.26]
15 31 ms 30 ms 30 ms v795.sff-d01.yhman.net.uk [194.81.2.75]
16 31 ms 31 ms 32 ms cpop1.shffu.yhman.net.uk [195.195.130.34]
17 34 ms 32 ms 32 ms 143.167.254.234
18 * * * Request timed out.
...
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Moved (with trepidation) to BT Infinity 2 for upload speed. Happy BE user for several years.